Temporarily use Python 2 for feedstock conversion

Ran into what appears to be a bug with `conda-build-all` and Python 3
during feedstock conversion. It appears the problem goes away with
Python 2. An issue has been filed upstream about the problem. In the
interim as this does workaround the issue, would like to switch to
Python 2 to clear the current batch of recipes. May be worthwhile
keeping this switch until the cause of the bug is better understood and
potentially fixed or worked around in a better way.

Based off of commit ( cd63d0e ).

[ci skip]

.CI/create_feedstocks

@@ -10,7 +10,7 @@ git checkout "${TRAVIS_BRANCH}"
 # Install Miniconda.
 echo ""
 echo "Installing a fresh version of Miniconda."
-curl -L https://repo.continuum.io/miniconda/Miniconda3-latest-MacOSX-x86_64.sh > ~/miniconda.sh
+curl -L https://repo.continuum.io/miniconda/Miniconda2-latest-MacOSX-x86_64.sh > ~/miniconda.sh
 bash ~/miniconda.sh -b -p ~/miniconda
 source ~/miniconda/bin/activate root