Merge pull request #93 from WordPress-Coding-Standards/develop

Add Travis CI integration and a pre-commit hook
Introduce a Function Restrictions Sniff, to handle restriction of different functions groups, each with its own error/warning message.
Merge branch 'develop', remote-tracking branch 'origin' into function-restriction-sniff
Improve FunctionRestrictionsSniff, convert to abstract class
Move existing groups to VIP\RestrictedFunctionsSniff ( switch_to_blog #82 and eval family #81 )
Add warnings about remote calls #85
Flag use of extract() #90
Convert remote calls sniffs to warning instead of errors, as per #85
Change abstract declaration of FunctionRestrictionsSniff, which broke PHPCS
Add Sniff class to check for variable occurances

This handles:
- Plain variables, ex: $foo
- Object vars, ex: $foo->bar
- Array members, ex: $foo['bar']
And it supports searching for all of the previous within double quoted strings as well.
Flag use of wp_users/usermeta #78
Merge branch 'develop' into variable-restrictions-sniff
Flag cron schedules less than 15 minutes
Fixes #84
Warn about __FILE__ for page registration #86
Flag use of custom roles #88
Restricting setcookie function #89
Merge branch 'variable-restrictions-sniff' into issue/89
Flag violations of caching constraints #89
Annotate statements in RestrictedFunctionsUnitTest
Add methods to unit test which yield false negatives
Note false negatives as OK
Add namespaced functions which also yield false negatives