Add /taxonomies routes

It is frequently desirable to know about all taxonomies, regardless
of the post type to which they are associated; it is also convenient
to be able to retrieve taxonomies from a base-level endpoint.

This adds the following routes to the taxonomies class:

- /taxonomies
- /taxonomies/(?P<taxonomy>\w+)
- /taxonomies/(?P<taxonomy>\w+)/terms
- /taxonomies/(?P<taxonomy>\w+)/terms/(?P<term>\w+)

Bug Reference: #198
Remove <type> argument from taxonomy routes

Per IRC conversation on 2014.05.26, the /taxonomies base route will take
precedence over the per-type endpoints. Removing the <type> parameter
will permit the existing routes to function, but moves towards having the
/taxonomies base routes become the canonical ones.
Update documentation to reflect /taxonomies routes

- Added routes/taxonomies.md defining existing taxonomy routes
- Updated guides/getting-started.md to clarify available methods (GET)
- Updated the schema.md file to reflect the base /taxonomy endpoints
Add unit tests for /taxonomies routes
Fix regression causing all taxonomies to be returned for all types

While the taxonomies routes are now type-independent, the post type
routes (e.g. /posts/types/post) return embedded taxonomy objects for
each taxonomy associated with that type. Removing the "types" argument
from the get_taxonomies method caused a regression where ALL
taxonomies would be returned for any post type endpoint.
Add test for add_taxonomy_data regression

This adds a test to verify that get_taxonomies only returns taxonomies
for the provided post type if a type is passed into the function. This
ensures that the taxonomies embedded into post type endpoint responses
will be accurate.

It also DRYs up the test code a bit to avoid repeating the methods for
filtering a taxonomy collection down to only "public" members.
Reinstate $types parameter for back-compat with 1.0

$types is only necessary in `get_taxonomies` and `add_taxonomy_data`;
however, we need to leave it in the argumentss list for ALL methods in
order to avoid breaking any plugins built to interoperate with v1.0.

get_taxonomy (singular), prepare_taxonomy, get_terms, get_term,
and prepare_term should all have their $type parameter removed in 2.0.
Add new methods for base /taxonomies routes & update tests

Because the new /taxonomies route have no $type parameter, and $type
cannot be removed without breaking back-compat, we need to add a new
set of route methods for the new, "correct" /taxonomies routes. To
minimize confusion, the old route method names were left as is, and
new methods added for each method which had previously taken a $type.
All the old methods are marked @deprecated and have a @see reference
to their successors.

New methods:

- `get_taxonomy` now wraps the new `get_taxonomy_object`
- `prepare_taxonomy` now wraps the new `prepare_taxonomy_object`
- `get_terms` now wraps the new `get_taxonomy_terms`
- `get_term` now wraps the new `get_taxonomy_terms`
- `prepare_term` now wraps the new `prepare_taxonomy_term`

The existing unit tests were changed to point to these new route methods.
Embed associated post type records in Taxonomy objects

This is the first pass at embedding a list of associated post types in
taxonomy records, as described in #197. Types are NOT embedded if they
would be added to a taxonomy record that is itself embedded.

@rmccue has proposed changing how the $_in_taxonomy behavior works to
use a "$context" variable, as in other methods; this commit should be
considered a work-in-progress until he has signed off on it.
Merge remote 'origin' branch 'master' into kadamwhite-add-taxonomy-base-route.

Conflicts:
	lib/class-wp-json-posts.php
	lib/class-wp-json-taxonomies.php
	plugin.php
Minor style fixes to match coding standards.
Hide deprecated routes from index
Mark legacy routes as deprecated
Pass deprecated errors via headers
Add missing whitespace
Test for missing parameters

These currently fail, but shouldn't. Huzzah!
Check parameters in the correct place

Update doesn't require the user data, creation does.
Work around WP data handling failure
Check that we're not mangling user passwords
Merge pull request #289 from WP-API/flip-user-params-check

Flip user parameters check for insert/update.  Closes #289.  Fixes #221.