Add option to allow deleting trailing whitespace (#251)

Add option g:NERDTrimTrailingWhitespace to allow deleting trailing
whitespace when uncommenting a line.

plugin/NERD_commenter.vim

@@ -64,6 +64,7 @@ call s:InitVariable("g:NERDRemoveExtraSpaces", 0)
 call s:InitVariable("g:NERDRPlace", "<]")
 call s:InitVariable("g:NERDSpaceDelims", 0)
 call s:InitVariable("g:NERDDefaultAlign", "none")
+call s:InitVariable("g:NERDTrimTrailingWhitespace", 0)
 
 let s:NERDFileNameEscape="[]#*$%'\" ?`!&();<>\\"
 
@@ -1419,6 +1420,15 @@ function s:RecoverStateAfterLineComment(state)
     endif
 endfunction
 
+" Function: s:TrimTrailingWhitespace(line) {{{2
+" This function removes all the trailing whitespace
+" Args:
+"   -line: the target line
+function s:TrimTrailingWhitespace(line)
+    let toReturn = substitute(a:line, '\s\+$', '', 'g')
+    return toReturn
+endfunction
+
 " Function: s:UncommentLines(topLine, bottomLine) {{{2
 " This function uncomments the given lines
 "
@@ -1511,6 +1521,10 @@ function s:UncommentLinesSexy(topline, bottomline)
 
         let theLine = s:ConvertLeadingWhiteSpace(theLine)
 
+        if g:NERDTrimTrailingWhitespace == 1
+            let theLine = s:TrimTrailingWhitespace(theLine)
+        endif
+
         " move onto the next line
         call setline(currentLine, theLine)
         let currentLine = currentLine + 1
@@ -1652,6 +1666,10 @@ function s:UncommentLineNormal(line)
 
     let line = s:ConvertLeadingWhiteSpace(line)
 
+    if g:NERDTrimTrailingWhitespace == 1
+        let line = s:TrimTrailingWhitespace(line)
+    endif
+
     return line
 endfunction