Fix continuation issue again

A spec was implemented for vim-ruby#139.

The issue this commit fixes is: vim-ruby#132.

By adding the `Symbol` group to the "string or syntax" pattern, some
continuations are fixed. It should not be added to the "string" pattern,
however.

indent/ruby.vim

@@ -31,9 +31,9 @@ set cpo&vim
 " 1. Variables {{{1
 " ============
 
-" Regex of syntax group names that are or delimit string or are comments.
+" Regex of syntax group names that are or delimit strings/symbols or are comments.
 let s:syng_strcom = '\<ruby\%(Regexp\|RegexpDelimiter\|RegexpEscape' .
-      \ '\|String\|StringDelimiter\|StringEscape\|ASCIICode' .
+      \ '\|Symbol\|String\|StringDelimiter\|StringEscape\|ASCIICode' .
       \ '\|Interpolation\|NoInterpolation\|Comment\|Documentation\)\>'
 
 " Regex of syntax group names that are strings.

spec/indent/continuations_spec.rb

@@ -130,4 +130,13 @@ def bar(
       # Next indents correctly
     EOF
   end
+
+  specify "continuation with a hanging comma" do
+    # See https://github.com/vim-ruby/vim-ruby/issues/139 for details
+    assert_correct_indenting <<-EOF
+      thing :foo
+      thing 'a',
+        'b'
+    EOF
+  end
 end