Use NSTextAlignmentCenter in place of UITextAlignmentCenter for iOS6 and later.
Fix analyzer warning: Attributes on method implementation and its declaration must match,
Fix analyzer warning: Unknown receiver 'FKBigTextField'; did you mean 'FKTextField'?
Use NSLineBreakMode in place of UILineBreakMode for iOS6 and later.
Fix analyzer warning: Cast of type 'SEL' (aka 'SEL *') to 'char *' is deprecated; use sel_getName instead.
Merge pull request #26 from quimarche/master

Fix compiler & analyzer warnings for iOS6.