filter out annoying warnings on cucumber steps

This patch filters out annoying warnings about "ambiguous first argument" that occur on typically formatted Cucumber step definitions like the following:

Given /^I am logged in$/ do
  pending
end

These are particularly annoying since the cursor gets moved to the first occurence of the warning every time you save.

Commands/Validate and Save.tmCommand

@@ -15,6 +15,12 @@ if compiler_ruby.length == 0
 end
 
 result = `#{compiler_ruby} -wc "$TM_FILEPATH" 2>&1`
+
+scopes = ENV['TM_SCOPE'].split
+if scopes.include? 'source.ruby.rspec.cucumber.steps'
+  result.gsub!(/^.+warning: ambiguous first argument; put parentheses or even spaces$/, '')
+end
+
 if result =~ /:(\d+):/
   print result
   TextMate.go_to :line => $1