Stabilization of v0.1.52

[Vojtech Polasek]

Hello all,
*Release of Content version 0.1.52 is scheduled for September 18th*, so 
I've created a stabilization branch for it.
Now is a good time to hunt for bugs and propose fixes for them. Starting 
today, merged Pull Requests should be assigned to milestone v0.1.53.
Bug fixes should be proposed to master and labeled "bugfix", they will 
be cherry-picked to the stabilization branch.
The next release 0.1.53 will happen on November 13th. Stabilization 
phase will start on November 2nd.
Best regards,

Vojta