Add Travis build with pystencils from pip

5 jobs for master in 3 minutes and 35 seconds (queued for 1 second)
Name Stage Failure
failed
minimal-ubuntu Test
 * [new tag]         0.1.2      -> 0.1.2
* [new tag] 0.1.3 -> 0.1.3
Checking out 086603bd as master...

Skipping Git submodules setup
Authenticating with credentials from /root/.docker/config.json
$ pip install -e .
/bin/bash: line 81: pip: command not found
ERROR: Job failed: exit code 1
failed
build-documentation Test
  Running setup.py develop for pystencils-autodiff
Successfully installed pystencils-0.2.6 pystencils-autodiff
$ export PYTHONPATH=`pwd`
$ mkdir html_doc
$ sphinx-build -W -b html doc html_doc

Application error:
config directory doesn't contain a conf.py file (doc)
ERROR: Job failed: exit code 1
failed
minimal-conda Test
src/pystencils_autodiff/backends/_pytorch.py             87     41     26      4    51%   8-10, 35->49, 36->37, 37-38, 45-53, 62->exit, 70-76, 99-103, 118-128, 131->132, 132-148
src/pystencils_autodiff/backends/_tensorflow.py 31 8 17 1 65% 47->46, 54-62, 65
src/pystencils_autodiff/backends/_tensorflow_cpp.py 0 0 0 0 100%
src/pystencils_autodiff/backends/_torch_native.py 101 29 57 10 66% 47->122, 47->exit, 51->53, 53->56, 68->81, 81-83, 104->116, 116-120, 125-126, 130->170, 132->exit, 133->exit, 139->140, 140, 144-175
-------------------------------------------------------------------------------------------------
TOTAL 597 169 300 43 70%

=================== 8 failed, 6 passed, 5 warnings in 6.69s ====================
ERROR: Job failed: exit code 1
failed
minimal-windows Test
base                     C:\Users\build\Miniconda3
pystencils_dev C:\Users\build\Miniconda3\envs\pystencils_dev

$ python -c "import numpy"
$ conda install pip

EnvironmentLocationNotFound: Not a conda environment: C:\Users\build\Miniconda3\envs\pystencils_dev

ERROR: Job failed: Process exited with: 1. Reason was: ()