switch iri column of AlternativeIri to text

Since some IRIs could be longer than 255 chars
this is necessary.
Merge pull request #541 from ontohub/534-fix_alternative_iri_varchar_issue

switch iri column of AlternativeIri to text
Better description of repository cloning methods in view.
Merge pull request #542 from ontohub/536-explain_clone_with_ssh_git

Better description of repository cloning methods in view. Fixes #536.
Updated Ruby version to 2.1.0.
Updated some gems.
Merge branch 'staging' into 476-number_of_ontologies_in_category_on_categories_index