gemspec update
* description
* summary
modify gitignore
implementation Criteria, Searchable
introduce spec environment
rspec for Criteria
* This version test dsatetime format yyyy/mm/dd-hh:mi:ss
* todo: support localized date/time format
this version support activerecord 3.2.x only
modify method name : associated_search -> associative_search
Searchable spec
Merge branch 'master' of github.com:dongoon/poor_man_search

Conflicts:
	lib/poor_man_search/searchable.rb
	poor_man_search.gemspec
	spec/support/test_models.rb