MIGRATED: Pattern aliases - introduces ability to register aliases for some often used regular expressions.

[tebruno99]

MIGRATED - See upstream comments

From Original PR: @HiveTraum gorilla#675 and gorilla#598
This feature introduces ability to register aliases for some often used regular expressions.

For example path as this:

/{category:[a-fA-F0-9]{8}-[a-fA-F0-9]{4}-4[a-fA-F0-9]{3}-[8|9|aA|bB][a-fA-F0-9]{3}-[a-fA-F0-9]{12}}/{product:[a-fA-F0-9]{8}-[a-fA-F0-9]{4}-4[a-fA-F0-9]{3}-[8|9|aA|bB][a-fA-F0-9]{3}-[a-fA-F0-9]{12}}

can be transformed into this

/{category:uuid}/{product:uuid}

You need just use register it

router := NewRouter()
router.RegisterPattern("uuid", "[a-fA-F0-9]{8}-[a-fA-F0-9]{4}-4[a-fA-F0-9]{3}-[8|9|aA|bB][a-fA-F0-9]{3}-[a-fA-F0-9]{12}")
router.Path("/{category:uuid}")
router.Path("/{product:uuid}")
router.Path("/{order:uuid}")
router.Path("/{user:uuid}")

1. New method RegisterPattern on Route struct
2. New method RegisterPattern on Router struct