Adding method to retrieve last modified version, and fix incorrect he…

…ader reference

Adds raw file method (urschrei#37)

Better iterfollow functionality (urschrei#38)
Adds method for single collection retrieval (urschrei#39)

Bugfixes and Pylint conformance

v1.0.0 release for Zotero API v3 compatibility

Updating setup

Move to Requests

Pyzotero now optionally maintains retrieved item order

Better error display, and file attachment methods

Adding unauthenticated library support

Query parameters can now be passed directly in methods

Example: Zotero.top(start = 5, limit = 3)