Appveyor improvements

[barsch]

• now building Py2.7/64 bit and Py3.6/32bit
• enabled rolling builds: whenever you do a new commit to the same branch OR pull request all current queued/running builds for that branch or PR are cancelled and the new one is queued.
• enabled fast finish: if first job has failed the entire build is marked as failed and no further jobs will start
• do not build feature branch with open Pull Requests

todo in future: add +TESTS magic to enable building the full matrix (py2.7 - py3.6, 32 and 64bit)

IMHO ready to merge see: https://ci.appveyor.com/project/obspy/obspy/build/1.0.4368-appveyor

[megies]

Great improvement to our CI, thanks @barsch!

[krischer]

Yea - looks great :)

now building Py2.7/64 bit and Py3.6/32bit

Contrary to that statement it currently tests both for 64 bit. Also should we maybe enable 32 and 64 bit builds? Appveyor is usually faster then travis so I don't think it will slow down our whole CI turnaround time.

[krischer]

For future reference: There is also this package here: https://github.com/pelson/Obvious-CI

conda-forge uses it for the appveyor builds and it would make it much easier. But as you already invested all the sweat I'd leave it as it is for now :) Also I don't think this can do the early termination and rolling builds which are really cool.

[barsch]

ups commented out the wrong version ;)

on appveyor we have only one job per time for the whole project - there is nothing parallel - so increasing the build time from 10 min to 80 min per checkin is quite a difference ... so I choose to offer only min and max python version ...

[barsch]

ok CI good - merging