Update UIColor+HexColors.m

Fixed the warning:

Implicit conversion from enumeration type 'enum NSMatchingFlags' to different enumeration type 'NSMatchingOptions' (aka 'enum NSMatchingOptions')
Merge pull request #1 from zacwitte/master

Update UIColor+HexColors.m
Merge branch 'master' of git://github.com/timd/UIColor-HexValues