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

Other changes were made

• Proper CI setup on Travis #298 & Appveyor #310.
• Generated headers are now in the repo, making compilation much
  simpler for packagers and other non developers #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

v2.0.0 beta 3

First attempt at producing release artifacts with Travis.