Adding link(), unlink() shorthand functions

[amreladawy]

As LINK and UNLINK have been accepted as allowed method, this PR for shorthand routing functions for them.

[akrabat]

My gut feeling is that link and unlink aren't commonly used enough.

Thoughts, @silentworks, @codeguy ?

[coveralls]

Coverage decreased (-0.2%) to 97.136% when pulling e6fa3c2 on amreladawy:patch-1 into 7d62584 on slimphp:3.x.

[coveralls]

Coverage decreased (-0.06%) to 97.255% when pulling 6e0ae51 on amreladawy:patch-1 into 7d62584 on slimphp:3.x.

[amreladawy]

Updated the unit test to cover the new functions.

[amreladawy]

I want to add LINK and UNLINKto the list of methods in the function any() but I am not sure if this would match the approach of avoiding literally listing allowed methods just like PR #2156

[geggleto]

@akrabat I was thinking the same thing, but I don't see any harm for the short-cuts.

[coveralls]

Coverage decreased (-0.06%) to 97.255% when pulling e5fa327 on amreladawy:patch-1 into 7d62584 on slimphp:3.x.

[coveralls]

Coverage decreased (-0.06%) to 97.255% when pulling e5fa327 on amreladawy:patch-1 into 7d62584 on slimphp:3.x.

[coveralls]

Coverage decreased (-0.06%) to 97.255% when pulling 09e99cd on amreladawy:patch-1 into 7d62584 on slimphp:3.x.

[silentworks]

I don't see any harm in writing it the long way by using map, I don't see this becoming a common thing anytime soon and don't feel we need to add a shortcut for it.