Updated Threads/Posts. Fixed related test.

* Added post_count and first_post_id indexes for thread
* Added linking of first post title to thread title
* Updated post test to work with latest changes
Added fix for allBoards.

* Child boards were being returned along side parent boards, as well
as nested under the parent boards. This commit fixes the issue
Updated Board tests (coverage/promises/BDD)

The boards test has now been upgraded to fully use Promises at every
step. It also now uses chai and BDD testing instead of TDD testing with
asserts. Each test is now atomic and are not reliant on any other test.

The tests in general cover more of the code than before but is still not
at 100% yet.
Fix for posts/thread postcount/first_post_id metadata.

* I was incorrectly storing metadata in the indexes db. This has been
fixed and post count and first post id for threads are now in the
metadata database.
Exposing post_count via thread find
Cleaning up promises in posts/threads
Added in support for posts.byThread

* Added in index to support posts.byThread as well
Removing async from posts db.

* Replaced async.concat with Promise.map
* close #3