Add minitest to gemspec so tests run

Not sure what the issue is here. Others have mentioned that minitest is not included with some vendored Rubies, so we must explicitly install it.

Author: shanecav84

rails-jquery-autocomplete.gemspec

@@ -16,6 +16,7 @@ Gem::Specification.new do |s|
   s.add_dependency('rails', '>= 3.2')
 
   s.add_development_dependency 'sqlite3-ruby'
+  s.add_development_dependency 'minitest'
   s.add_development_dependency 'mongoid',      '>= 2.0.0'
   s.add_development_dependency 'mongo_mapper', '>= 0.9'
   #s.add_development_dependency 'mongo',        '~> 1.6.2'