Release Mozart2 version 2.0.1

I am very pleased to announce that version 2.0.1 of Mozart2 has been
released.  This is the first stable release of Mozart2, all users are
encouraged to upgrade.

This version comes with several bugfixes

* Error out on duplicate fields in records mozart#285.
* Fix incorrect error message on fullUnify failure mozart#312.
* Fix race condition at VM exit mozart#307. This fixes several failures like
  hanging at exit, crashes during execution and persisting child
  processes.
* Fix crash when browsing cyclically linked cells mozart#167.
* Fix the build on Windows mozart#310.

Other changes were made

* Proper CI setup on Travis mozart#298 & Appveyor mozart#310.
* Generated headers are now in the repo, making compilation much
  simpler for packagers and other non developers mozart#309.
* Some cleanup to reduce compiler warnings.
* Updates to build with LLVM/CLang 4.0 and Boost 1.67.

I would like to thank @azarzadavila for his extensive work, making this
release possible. He also worked on an OPI plugin for SublimeText [1],
so double cheers for him!
Thanks also to @sjrd, @eregon and @sjmackenzie for their advices and
more generally their interest in these changes.

[1] mozart/sublime-oz#1

Fix travis releases

Version 2.0.0 alpha 0.