Use search pattern as delimiter if empty regex is given

Close #78

autoload/easy_align.vim

@@ -829,10 +829,11 @@ function! s:valid_regexp(regexp)
 endfunction
 
 function! s:test_regexp(regexp)
-  if !s:valid_regexp(a:regexp)
-    call s:exit('Invalid regular expression: '. a:regexp)
+  let regexp = empty(a:regexp) ? @/ : a:regexp
+  if !s:valid_regexp(regexp)
+    call s:exit('Invalid regular expression: '. regexp)
   endif
-  return a:regexp
+  return regexp
 endfunction
 
 let s:shorthand_regex =

test/commandline.vader

@@ -105,6 +105,14 @@ Expect:
   ap><pl><e;><:;><;b><an><an><a:><:c><ak>e
   da><ta><;;><ex><ch><an><ge><:;><::><fo> <rm><at
 
+Execute (Use current search pattern as delimiter if empty regular expression is given):
+  /an
+  %EasyAlign*//
+
+Expect:
+  apple;:;;b an  an a::cake
+  data;;exch an ge:;::format
+
 Given javascript (json):
   var jdbc = {
     // JDBC driver for MySQL database: