Split up creating, deleting and updating diag requests for clarity.

Now reads the 'action' field of an incoming diagnostic request.
Don't allow updating recurring diag requests (KISS).

Just delete it and re-add. For a proper update we would need a way to
tell exactly which fields you want to update, and from there things get
ugly.
Return a status response for all diagnostic request commands.
Add tests for adding non-recurring diag requests and cancelling.
Split up creating, deleting and updating diag requests for clarity.

Now reads the 'action' field of an incoming diagnostic request.
Don't allow updating recurring diag requests (KISS).

Just delete it and re-add. For a proper update we would need a way to
tell exactly which fields you want to update, and from there things get
ugly.
Return a status response for all diagnostic request commands.
Add tests for adding non-recurring diag requests and cancelling.
Make sure diag command responses have no 'message'.
Work around lack of symlinks on the shared folder in Vagrant in Windows.

Fixed #259.
Note that changing PATH didn't seem necessary for VirtualBox in Win8.
Merge branch 'master' into next
Merge remote-tracking branch 'origin/action-field-diag-request' into action-field-diag-request

Conflicts:
	src/commands.cpp
Merge branch 'action-field-diag-request' into next
Add badge to show status of docs at RTD.
Add tests for CAN and diag JSON payloads without 0x prefix.

Fixed https://github.com/openxc/openxc-android/issues/163
Update to building with MPIDE 20140821 and new Arduino-Makefile.
Use MIN/MAX macros instead of std::min/max for portability.

The latest MPIDE build tools don't have this std library.
Update compiler flags to work with latest MPIDE.
Fix outdated env variable in docs for binary output.