Use travis native cache

[Kojoley]

As per https://docs.travis-ci.com/user/caching/

[jenshnielsen]

It's not clear from the travis docs that pip caches $HOME/Library/Caches/pip which is the pip cache directory on OSX.

[Kojoley]

As per travis-ci/travis-ci#4011 it is now support OSX too.

[jenshnielsen]

I know that caching is supported on OSX that's why I added $HOME/Library/Caches/pip to the list of cached directories. But the documentation that you link to says that doing

cache:
  - pip

only adds

~/.cache/pip

to the cache and not $HOME/Library/Caches/pip

I can't see anything in the docs or the issue that you are linking to that indicates otherwise.

If you compare the OSX build of your PR to one of the Linux ones it seems to confirm that.
Linux:
https://s3.amazonaws.com/archive.travis-ci.org/jobs/146969225/log.txt
OSX:
https://api.travis-ci.org/jobs/146969231/log.txt?deansi=true

In the osx build all the dependencies are redownloaded.

[Kojoley]

Hmm. Even ccache was not used and stored on OSX

Edit: on Linux ccache does not work too (it requires language: c, see travis-ci/travis-ci#5853)

[Kojoley]

I have found that apt-get and brew currently is not cached. Should I reuse this PR or open a new one? (this seems can be done with cache: apt)

[jenshnielsen]

Good catch. I think it's fine to use this one you can always change the title in the github web interface

[Kojoley]

Sigh. It is not possible now travis-ci/travis-ci#5876

[Kojoley]

Summary:

• There is no way to cache apt-get and brew packages with cache: apt
  (it is no longer exists APT caching doesn't work for packages installed with the APT addon travis-ci/travis-ci#5876)

• apt-get is fast as is Fetched 158 MB in 3s (46.5 MB/s) (sometimes it slowdowns to 15 sec)

• Storing brew cache gives no or insignificant speed up (even makes cache store phase much longer)

• cache: ccache is not supported with language: python (ccache doesn't work for Python projects travis-ci/travis-ci#5853)

• cache: pip does not work on OSX

• global cannot be used in cache (like in env) (workarounded with copy-paste):

  cache:
    global:
      pip: true
      directories:
        - $HOME/.cache/matplotlib
  
  matrix:
    include:
      - os: osx
        osx_image: xcode7.3
        cache:
          pip: false
          directories:
            - $HOME/Library/Caches/pip

I have updated appveyor.yml with comments about results above.