Tdxlib

This release includes several bugfixes and a few new features.

Major Bugs Fixed:
- Handles 401's gracefully on long-running sessions (only when password stored in .ini file)
- search_assets() now handles assets with no serial number
- update_assets() now does not clear all custom attribute data unless explicitly instructed to

Minor features added:
- Added functions and tests for asset management, including:
- Locating and updating asset/CI custom attributes
- Getting assets by various attributes (requesting dept, location, room, etc)

There were a few ticket attributes changed in the release of TDX 11.

This fixes ticket validation for those new attributes.

This release includes changes that:

* gracefully handle rate-limiting from TDX
* implement most of the remaining ticket methods, including:
* ticket tasks
* reassignment
* rescheduling
* custom ticket statuses
* implement lots of bugfixes, especially in:
* handling custom attributes
* partial matches of names when searching for objects
* editing tickets
* finish up unit test writing in the tickets module
* include contributing guidelines
* reorganize file structure
* rework one of the example scripts so that it reflects current capabilities of tdxlib
* implement a templated testing system that is easily customizable for any contributer