Merge pull request #379 from olasundell/master

The Makefile is now OSX and Linux aware
Revert "Merge pull request #379 from olasundell/master"

This reverts commit 5ec216800146df0503685e544210ee1daef8d2a1, reversing
changes made to db65f55284a7e45e586defa1dbe280d5f6f2e37d.
Releasing 2.3.0
Preparing 2.3.1 release;
Merge pull request #398 from MuMech/dev

MechJeb 2.3.1 release
Removed revision checking from CompatibilityChecker.
Remove Joke
Add option for AoA limiting in ascent guidance
Allow changing SmartASS target while another module steers
checkpoint on aoa limit in attitude controller
spaceplane mode checkpoint