added ability for parameters to be passed to searchable_by

added specs for '#is_searchable?' and '#searchable_values' class methods
made '#searchable_by' take a splat named values as parameters
pass values to a class variable called '@searchable_values'
added 'searchable_values' attr_reader to is_searchable module
updated schema in spec_helper to have table :searchable_models contain multiple columns
added ability to search by any of the '@searchable_values'

added specs for '#find_by_value'
added class method '#find_by_value' to IsSearchable module
'#find_by_value' takes a value as the argument
it itterates through all of the '@searchable_values' checking the database for any of the searchable_values that contain the give argument
Merge pull request #10 from zachmokahn/01_add_methods_to_active_record_objects

01 add methods to active record objects