add invalid cases to UriRetrieverTest, making the Test fail
fix immediate return condition in Undefined constraint
fix mock UriRetriever return value - json object instead of json string
fix code style
fixed Exception message on JSON_ERROR_SYNTAX decode error
Merge pull request #54 from alexmmm/fix-uri-retriever-test

Fix UriRetriever test
Merge pull request #60 from dazz/fix-exception-message

bugfix: JsonDecodingException message
Add AbstractRetriever and remove duplicate implementations through inheritence
Add coverage directory and IDE files to gitignore
Remove tabs/whitespace. Add unit test coverage. Add code comments.
Add docs make linkcheck to travis-ci
Add travis-ci install docs dependencies
Add travis-ci install docs dependencies
Add PHPDocumentor 2 to travis-ci
Properly resolve relative URIs with fragments: "base.json#/definitions/foo"
HACK: limit recursive expansion to 7 levels
show path info in invalid-schema exception
HACK: do not validate MIME type of schema files from json-schema.org
cache fetched schema object; needed for recursively nested schemas
Merge branch 'pull-71'

* pull-71:
  HACK: limit recursive expansion to 7 levels