Add .arb, Active Admin files views extensions, to be considered Ruby …

…file (#16)

vimrc

@@ -454,7 +454,7 @@ set statusline^=%{get(g:,'coc_git_status','')}%{get(b:,'coc_git_status','')}%{ge
 " run the above commands only if vim is compiled with autocmd
 if has("autocmd")
   autocmd BufWritePost .vimrc source $MYVIMRC " apply .vimrc settings on save
-  autocmd BufWritePre *.rb,*.erb,*.html,*.js,*.css,*.php,*.py,*.json :call <SID>StripTrailingWhitespaces() " remove trailing white spaces before saving (only in specified filetypes)
+  autocmd BufWritePre *.rb,*.arb,*.erb,*.html,*.js,*.css,*.php,*.py,*.json :call <SID>StripTrailingWhitespaces() " remove trailing white spaces before saving (only in specified filetypes)
 endif
 
 " function to remove trailing white space (while saving cursor position)