remove redundant task

Two rake tasks that were running the same exact thing, spec and test
refactored methods for semantic understanding

spec/lib/searchable_spec
added spec to test that '#searchable?' is an alias of '#is_searchable?' for searchable and non-searchable models
added spec to test that '#search_for' is an alias of '#find_by_value' for searchable and non-searchable models
added a test model that has the attribute '#finable_by' instead of '#searchable_by'
added spec to test that '#findable_by' is an alias of '#searchable_by'

spec/spec_helper
added 'findable_models' table to the test schema to test the '#finable_by' alias

lib/searchable/search_helper
moved 'self#is_searchable?'' from the ActiveRecord::Base class to the Searchable::SearchHelper::ClassMethods module
added alias '#searchable?' to the '#is_searchable?''
added alias '#findable_by' to '#searchable_by'

lib/searchable/is_searchable
added alias '#search_for' to '#find_by_value'
Merge pull request #14 from zachmokahn/04-refactoring_for_semantics

04 refactoring for semantics