JSON::Schema::Loader
Wedge JSON::Schema::Loader into place in Validator

Conflicts:
	lib/json-schema/validator.rb
Document JSON::Schema::Loader in the README

Prolly got some textile syntax a bit wrong, and the link to the yard
docs won't work prior to this being merged.
Revert some unnecessary changes

I'll submit a separate PR to add pry (and pry-byebug) as dependencies in
the Gemfile.

Reverted some changes I made to attributes/ref.rb that would conflict
with #186.
Simplify reset of schema_loader in tests
Made sure that all of the test gemfiles are loading all dev dependencies

As things were (with all dev dependencies defined in the Gemfile) the
additional gemfiles in ./gemfiles (used for testing optional
dependencies) were not requiring additional devdependencies, such as
minitest (they were still passing, but were probably using a different
version of minitest to the main test runs)
Switched on quirks mode for json gem

This makes it behave:

1. More like multi json and yajl, which can parse scalar values (not
just hashes or arrays)
2. More correctly, in terms of the latest json rfc (rfc7159)*

Incidentally both multi_json and rails turn on quirks mode by default.

But there are a few other reasons for doing this - before, if json schema
was passed a string, then parsing would fail and the string would be
passed into the validator as a string. But that string could contain an
integer or a float value. That's clearly not the correct behavior.
Let's use webmock as described in the readme

Instead of requiring it lots of times, and calling it when we don't need
to
Added a "parse_data" option, which can be set to false to skip any
attempt to parse the data
Made sure we use a fairly recent version of json-gem on ruby 1.9

Seems like some older versions of the json gem segfault if they're
passed anything other than a string. We rely on json raising an error if
it's not given a string (in Validator#initialize_data)
Rename Loader -> Reader
Merge pull request #196 from iainbeeston/test_coverage

Fix test runs for optional dependencies
Merge pull request #175 from pd/schema-loader

JSON::Schema::Reader
WebMock is on globally now; no need to disable it

Introduced by conflicts in how #175 and #196 juggled webmock usage.

Closes #207.
Handle exception types for alternate JSON backends
Merge pull request #208 from pd/leave-webmock-enabled

WebMock is on globally now; no need to disable it
Refactored tests that catch parse errors to share the same code
Merge pull request #210 from iainbeeston/assert_raise_parser_error

Refactored parser error code
ref issue with usage of convert_path
Always use absolutized URIs without fragment hash as keys for registered schemas