Bidshandler

With v0.2 of BIDSHandler it is now possible to query BIDS-compliant archives.
The readme and documentation has also been completely reworked to have the entire API documented automatically.

BIDSHandler should also have basic capabilities with MRI and EEG data.

API Changes:
- The `BIDSFolder` object was renamed to `BIDSTree`

New Features:
- Query functionality (see documentation for more details)
- Xml mapping of folder is able to be generated using `BIDSTree.generate_map`

Initial release of BIDSHandler.

Currently BIDSHandler is designed primarily for MEG data, however it should work completely fine with EEG data also. (MRI is very unlikely).
The main focus of this initial release is on the basic functionality.
BIDSHandler can load a BIDS-compatible folder and map out the structure of it, loading in any project, subject, session and scan details which can be easily retrieved.
BIDS data can also be manipulated to be moved from one location to another, so merging of BIDS data across locations can be completed very easily.