Fix text centering bug.
Fix text centering bug.

ywzw2013/JTSImageViewController,IdeasOnCanvas/JTSImageViewController,Ethan-Z/JTSImageViewController,Kingside/JTSImageViewController,FanPortal/JTSImageViewController,lintaoSuper/JTSImageViewController,ainopara/JTSImageViewController,mattprowse/JTSImageViewController,GeorgesAlkhouri/JTSImageViewController,jogabo/JTSImageViewController,jonesgithub/JTSImageViewController,bulusoy/JTSImageViewController,iosphere/JTSImageViewController,tokorom/JTSImageViewController,jaredsinclair/JTSImageViewController,colemancda/JTSImageViewController,mash/JTSImageViewController,clooth/JTSImageViewController,atone/JTSImageViewController,ello/JTSImageViewController,hoanganh6491/JTSImageViewController,larcus94/JTSImageViewController,caoer/JTSImageViewController,ElfSundae/JTSImageViewController