Update dalvikName, dalvikString and dalvikLabel in syntax/smali.vim

更新 syntax/smali.vim 中的 dalvikName, dalvikString and dalvikLabel
引用 lilydjwg 的修改
参见 smali: update dalvikName and dalvikLabel
https://github.com/lilydjwg/dotvim/commit/ceea56d765cd343437348d9618e513b1b2dbe057
和 smali: fix string highlight
https://github.com/lilydjwg/dotvim/commit/f57c5fe0562479e0267cac47f502a3e51a58ea8a
Refine ftdetect/smali.vim

完善 ftdetect/smali.vim
Add ftplugin/smali.vim

增加 ftplugin/smali.vim
取自 https://github.com/alderz/smali-vim/blob/master/ftplugin/smali.vim
Add README.md

增加 README.md