Update API routes documentation to correctly mention middlewares

[timneutkens]

Previously we said "Micro middlewares" but Next.js does not use micro. This would confuse users as both Next.js and Micro were created by ZEIT and Next.js API routes have different semantics than Micro handlers.

I've updated the docs to show how to use the cors middleware that's generally used in express apps.

[ijjk]

Stats from current PR

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General

	zeit/next.js canary	timneutkens/next.js fix/NEXT-135	Change
buildDuration	10.7s	10.8s	⚠️ +75ms
nodeModulesSize	54.8 MB	54.8 MB	✓

Client Bundles (main, webpack, commons)

	zeit/next.js canary	timneutkens/next.js fix/NEXT-135	Change
main-HASH.js gzip	5.77 kB	5.77 kB	✓
webpack-HASH.js gzip	746 B	746 B	✓
de003c3a9d30..8eb0.js gzip	9.78 kB	9.78 kB	✓
framework.HASH.js gzip	39.1 kB	39.1 kB	✓
Overall change	55.4 kB	55.4 kB	✓

Client Bundles (main, webpack, commons) Modern

	zeit/next.js canary	timneutkens/next.js fix/NEXT-135	Change
main-HASH.module.js gzip	4.78 kB	4.78 kB	✓
webpack-HASH..dule.js gzip	746 B	746 B	✓
de003c3a9d30..dule.js gzip	6.71 kB	6.71 kB	✓
framework.HA..dule.js gzip	39.1 kB	39.1 kB	✓
Overall change	51.4 kB	51.4 kB	✓

Legacy Client Bundles (polyfills)

	zeit/next.js canary	timneutkens/next.js fix/NEXT-135	Change
polyfills-HASH.js gzip	26.3 kB	26.3 kB	✓
Overall change	26.3 kB	26.3 kB	✓

Client Pages

	zeit/next.js canary	timneutkens/next.js fix/NEXT-135	Change
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hooks.js gzip	664 B	664 B	✓
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link.js gzip	1.89 kB	1.89 kB	✓
routerDirect.js gzip	279 B	279 B	✓
withRouter.js gzip	278 B	278 B	✓
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Client Pages Modern

	zeit/next.js canary	timneutkens/next.js fix/NEXT-135	Change
_app.module.js gzip	594 B	594 B	✓
_error.module.js gzip	2.08 kB	2.08 kB	✓
hooks.module.js gzip	370 B	370 B	✓
index.module.js gzip	212 B	212 B	✓
link.module.js gzip	1.48 kB	1.48 kB	✓
routerDirect..dule.js gzip	271 B	271 B	✓
withRouter.m..dule.js gzip	270 B	270 B	✓
Overall change	5.28 kB	5.28 kB	✓

Client Build Manifests

	zeit/next.js canary	timneutkens/next.js fix/NEXT-135	Change
_buildManifest.js gzip	61 B	61 B	✓
_buildManife..dule.js gzip	61 B	61 B	✓
Overall change	122 B	122 B	✓

Rendered Page Sizes

	zeit/next.js canary	timneutkens/next.js fix/NEXT-135	Change
index.html gzip	917 B	917 B	✓
link.html gzip	926 B	926 B	✓
withRouter.html gzip	915 B	915 B	✓
Overall change	2.76 kB	2.76 kB	✓

---

Serverless Mode (Decrease detected ✓)

General

	zeit/next.js canary	timneutkens/next.js fix/NEXT-135	Change
buildDuration	11.7s	11.7s	⚠️ +69ms
nodeModulesSize	54.8 MB	54.8 MB	✓

Client Bundles (main, webpack, commons)

	zeit/next.js canary	timneutkens/next.js fix/NEXT-135	Change
main-HASH.js gzip	5.77 kB	5.77 kB	✓
webpack-HASH.js gzip	746 B	746 B	✓
de003c3a9d30..8eb0.js gzip	9.78 kB	9.78 kB	✓
framework.HASH.js gzip	39.1 kB	39.1 kB	✓
Overall change	55.4 kB	55.4 kB	✓

Client Bundles (main, webpack, commons) Modern

	zeit/next.js canary	timneutkens/next.js fix/NEXT-135	Change
main-HASH.module.js gzip	4.78 kB	4.78 kB	✓
webpack-HASH..dule.js gzip	746 B	746 B	✓
de003c3a9d30..dule.js gzip	6.71 kB	6.71 kB	✓
framework.HA..dule.js gzip	39.1 kB	39.1 kB	✓
Overall change	51.4 kB	51.4 kB	✓

Legacy Client Bundles (polyfills)

	zeit/next.js canary	timneutkens/next.js fix/NEXT-135	Change
polyfills-HASH.js gzip	26.3 kB	26.3 kB	✓
Overall change	26.3 kB	26.3 kB	✓

Client Pages

	zeit/next.js canary	timneutkens/next.js fix/NEXT-135	Change
_app.js gzip	1.09 kB	1.09 kB	✓
_error.js gzip	2.97 kB	2.97 kB	✓
hooks.js gzip	664 B	664 B	✓
index.js gzip	222 B	222 B	✓
link.js gzip	1.89 kB	1.89 kB	✓
routerDirect.js gzip	279 B	279 B	✓
withRouter.js gzip	278 B	278 B	✓
Overall change	7.39 kB	7.39 kB	✓

Client Pages Modern

	zeit/next.js canary	timneutkens/next.js fix/NEXT-135	Change
_app.module.js gzip	594 B	594 B	✓
_error.module.js gzip	2.08 kB	2.08 kB	✓
hooks.module.js gzip	370 B	370 B	✓
index.module.js gzip	212 B	212 B	✓
link.module.js gzip	1.48 kB	1.48 kB	✓
routerDirect..dule.js gzip	271 B	271 B	✓
withRouter.m..dule.js gzip	270 B	270 B	✓
Overall change	5.28 kB	5.28 kB	✓

Client Build Manifests

	zeit/next.js canary	timneutkens/next.js fix/NEXT-135	Change
_buildManifest.js gzip	61 B	61 B	✓
_buildManife..dule.js gzip	61 B	61 B	✓
Overall change	122 B	122 B	✓

Serverless bundles Overall decrease ✓

	zeit/next.js canary	timneutkens/next.js fix/NEXT-135	Change
_error.js gzip	293 kB	293 kB	⚠️ +55 B
404.html gzip	1.32 kB	1.32 kB	✓
hooks.html gzip	958 B	958 B	✓
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link.js gzip	301 kB	301 kB	-43 B
routerDirect.js gzip	300 kB	300 kB	-277 B
withRouter.js gzip	300 kB	299 kB	-495 B
Overall change	1.49 MB	1.49 MB	-823 B