Release 2.0.

* Linter UI now implemented as an HTML Web Application using AngularJS.
* Linting services now operated using JSON requests, as described in the About section.
* Requests are cached using HTTP caching semantics and Rack::Cache.
* Verfiy SSL is now an option, rather than always being applied.
* Updated schema.org examples for the 1.92 \"Venkman\" release.
Finish 2.0-Gemfile-lock
Version 2.1.
Use updated rdf-reasoner with OGP literal datatype support.
This addresses issue #19.
Allow language-tagged string to match schema:URL.
Update dependency on rdf-reasoner to 0.2.1.
Fix test for language-taged URL.
Release 2.1.

* Use updated rdf-reasoner with OGP literal datatype support. This addresses issue #19.