delete_collection now accepts a list of collections to delete.

Conflicts:
	pyzotero/zotero.py
Revert "delete_collection now accepts a list of collections to delete."

This reverts commit 637025b2702084d34110a2bc4320e04e9e3f3e1f.

It was done in the wrong branch.
delete_collection now accepts a list of collections to delete.

Conflicts:
	pyzotero/zotero.py
Merge branch 'delete_multiple_collections' into dev
Fix delete_collection headers for Py3
Updating delete_collection docs
Attempting to use pkg_resources to grab version
Adds possibility of downloading PDF attached files
Avoid setting format parameter when getting a file
file method can now return raw content for more types than just PDF
Updated doc to include file method
Adds check to iterfollow to avoid unwanted exception
Adds collection method
Adds missing test PDF
Adds collection method test
Adds collection method documentation
Fixs missing comma
Merge remote-tracking branch 'mpao/fix_iterfollow' into dev
Merge remote-tracking branch 'mpao/dev' into dev

This PR incorporates the "file" method to pyzotero that will pull the raw content
of the file and return it as a binary string.
This also includes the corresponding test and documentation update.
Version bump