Adds skeleton for pre- and post-processors.
Merge master and processors branches
Small bug fix
PEP8 fix
Refactoring calling pre-, post-processor functions
Tests for preprocessor functions
Fix in catching exceptoins
Records the range of issues that this branch fixes.
Cleans up test code.
Adds missing tests for helper functions.
Replaces two identical exceptions with a single one.
Clears up preprocessing and postprocessing code and tests.
Adds documentation for preprocessing and postprocessing.
Removes extra newline.
Clarifies documentation string.
Corrects incorrect versionadded:
Adds documentation.
Adds skeleton for pre- and post-processors.

Conflicts:
	CHANGES
	flask_restless/helpers.py
	flask_restless/views.py
Small bug fix
PEP8 fix