Constrain rspec to v2.14.x to avoid deprecation warnings

I think this must've been the version I was using when I was first developing
in this repo.

Author: floehopper

method_log.gemspec

@@ -26,5 +26,5 @@ Gem::Specification.new do |s|
   s.add_dependency 'trollop'
 
   s.add_development_dependency 'rake'
-  s.add_development_dependency 'rspec'
+  s.add_development_dependency 'rspec', '~> 2.14.0'
 end