Release vibe.d 0.7.31

[Sönke Ludwig via Digitalmars-d-announce]

This release is a backport release of the smaller changes that go into 
0.8.0. The 0.7.x branch will continue to be maintained for a short 
while, but only bug fixes will be included from now on. Applications 
should switch to the 0.8.x branch as soon as possible.

Main changes over 0.7.30:

   - Compiles on the latest DMD version (2.068.x-2.072.0)
   - Introduces a number of forward compatibility declarations for the
     0.8.0 branch and vibe-core
   - The HTTP server received various improvements
   - All changes: https://vibed.org/blog/posts/vibe-release-0.7.31

DUB package:
https://code.dlang.org/packages/vibe-d/0.7.31