add functional tests for graphs controller.
move MappingError into the class and rename it.
add submethod tests for GraphDataFetcher.
add logic-specific tests for GraphDataFetcher.
update bundled gems.
add factory for links.
add ontology-specific tests.
add missing GraphDataFetcher mappings.
replace remove shoulda matchers with asserts

- since shoulda 2.0 some matchers have been
  [remove](http://robots.thoughtbot.com/post/47031676783/shoulda-matchers-2-0).