Fix primary key identification

_primary_key_name was finding the table column name, however it should
find the attribute name of the model
Merge pull request #176 from logandk/custom-column-names-upstream

Fix primary key identification
Records change due to previous commit.
Fixes typo in documentation.
Sorts items in changelog in increasing numerical order by GitHub issue number.
Adds test for adding multiple instances of association proxy in POST.
Fix issue #164.
Allow patching related models - fixes #173. Allow creation of duplicate instances when no unique index exist - fixes #172.

Conflicts:
	flask_restless/views.py
Style and documentation improvements.
Adds issues fixed to changelog.
Trims line to 79 characters.
Adds exclude_ and include_relations back in.
allow disabling deep results per-request