migrate to using miniconda

[applio]

Anaconda is great though I suggest that the closely related Miniconda is even more on target for Heroku deployments because it seeks to install only the packages required (whereas Anaconda has a larger core set of packages that come as part of any install, before further customization).

The proposed changes in this pull request provide:

• smaller slug sizes (a show-stopping issue when the slug size is too large for Heroku's 300Mb limit),
• still use conda-requirements.txt file in the same way to control binary package installs,
• permits processing of requirements.txt via pip after conda has installed its packages for anything not easily installed via conda (but still available via pip),
• by pointing at http://repo.continuum.io/miniconda/Miniconda-latest-Linux-x86_64.sh this buildpack is kept up-to-date over time without impact to the versions specified in various requirements.txt files,
• addresses Open Issue 1 (https://github.com/kennethreitz/anaconda-buildpack/issues/1) by keeping separate controls for conda and pip while supporting both because the format required by conda --file is distinct from the format required by pip -r and so the creation of conda-requirements.txt should really be managed via conda itself (via conda list -e in the user's current working conda environment),
• addresses Open Issue 3 (https://github.com/kennethreitz/anaconda-buildpack/issues/3) due to changes in how conda is invoked here as well as changes in conda over the last few months,
• enables installation of combinations of scipy+numpy that have been problematic via pip,
• similarly enables installation of scikit-image (which was not possible for me simply via a single pip requirements.txt pass).

I realize you likely haven't touched this project in some time. There are still other aspects of the scripts in this buildpack that deserve further investigation but I believe the changes I'm proposing already result in a generally useful/reusable package. Thank you for having taken the time to put together this buildpack in the first place -- without your efforts I would never have been inspired to make this work.

[bnjmnt4n]

:+1: @applio It looks like you’ve done some great work. Question: have you tested your changes and made sure it works? If so, I look forward to this being merged!

[bnjmnt4n]

I noticed that you commented out the mv line, I don’t think it would work without that.

[applio]

@d10 It's been working well for me with regular use on existing and on new sites on heroku over the last 2 months.

That mv is unnecessary when miniconda is explicitly told to install into /app in the first place in the line right before it:

./Miniconda-latest-Linux-x86_64.sh -b -p /app/.heroku/miniconda

Thanks for taking a careful look at it all.

[bnjmnt4n]

Ah, didn’t notice that. :+1: for merging this in. @applio do you mind if I use your fork for my project until it gets merged?

[applio]

@d10 Go for it -- no reason to wait on the merge.

[kennethreitz]

I never saw this! Looks like we implemented almost identical changes :)

[kennethreitz]

taking bits and pieces from this :)

[bnjmnt4n]

@kennethreitz awesome :)