Remove "/" from list of allowed characters before if

This means that dividing a number by the results of an if-clause won't
work right, but at least regular expressions will.

Discussed in #254

syntax/ruby.vim

@@ -242,7 +242,7 @@ if !exists("b:ruby_no_expensive") && !exists("ruby_no_expensive")
   " statements without 'do'
   syn region rubyBlockExpression       matchgroup=rubyControl	  start="\<begin\>" end="\<end\>" contains=ALLBUT,@rubyNotTop fold
   syn region rubyCaseExpression	       matchgroup=rubyConditional start="\<case\>"  end="\<end\>" contains=ALLBUT,@rubyNotTop fold
-  syn region rubyConditionalExpression matchgroup=rubyConditional start="\%(\%(^\|\.\.\.\=\|[{:,;([<>~\*/%&^|+=-]\|\%(\<[_[:lower:]][_[:alnum:]]*\)\@<![?!]\)\s*\)\@<=\%(if\|unless\)\>" end="\%(\%(\%(\.\@<!\.\)\|::\)\s*\)\@<!\<end\>" contains=ALLBUT,@rubyNotTop fold
+  syn region rubyConditionalExpression matchgroup=rubyConditional start="\%(\%(^\|\.\.\.\=\|[{:,;([<>~\*%&^|+=-]\|\%(\<[_[:lower:]][_[:alnum:]]*\)\@<![?!]\)\s*\)\@<=\%(if\|unless\)\>" end="\%(\%(\%(\.\@<!\.\)\|::\)\s*\)\@<!\<end\>" contains=ALLBUT,@rubyNotTop fold
 
   syn match rubyConditional "\<\%(then\|else\|when\)\>[?!]\@!"	contained containedin=rubyCaseExpression
   syn match rubyConditional "\<\%(then\|else\|elsif\)\>[?!]\@!" contained containedin=rubyConditionalExpression