Bump version to 0.8.4
Bump version to 0.8.4

ywzw2013/SECoreTextView,kishikawakatsumi/SECoreTextView,yingzhuo1314/SECoreTextView,qskycolor/SECoreTextView,randyeasy/SECoreTextView,HarrisLee/SECoreTextView,xiaonan0527/SECoreTextView