Fix TextWidth spec for Ruby 1.9.3

The test was failing since `#lines` returns an Enumerator in 1.9.3.
Ensure it is an array.

Author: sds

spec/overcommit/hook/commit_msg/text_width_spec.rb

@@ -6,7 +6,7 @@
   subject { described_class.new(config, context) }
 
   before do
-    context.stub(:commit_message_lines).and_return(commit_msg.lines)
+    context.stub(:commit_message_lines).and_return(commit_msg.lines.to_a)
     context.stub(:empty_message?).and_return(commit_msg.empty?)
   end