add cli support for --transform-key to support mode's like production…

[serapath]

…/staging/etc..

Details see: #1706 (comment)

[serapath]

Can this be merged anyway even though tests are failing?
This seems to be not related to my pull request at all.

Only bin/advanced.txt, readme.markdown and bin/args.js were touched.
In bin/args.js it's just one more command line option - so i don't see how this can possibly responsible for the breaking test.

[serapath]

Maybe it would be even better to name it --mode or short -m instead, because --transform-key is kind of long.

[serapath]

@substack another 2 pull request to fix a problem with dependencies that do not specify the alternative --transform-key. They affect browserify and module-deps.

• Fix: set package.json#browserify#transform as fallback option when using --transform-key #1721
• allow a dependent module to specify a default transform field module-deps#131