revert PR9; add --no-deps to pip wheel
Revert PR9; it was never actually needed in the first place it just fixed an
issue by side effect.
1) add --no-deps to pip wheel step in order to avoid building wheels for
dependencies. This also addresses the issues raised in PR #11.
2) Modify the pip install step across platforms to allow installation of
dependencies from the index. (This is required since we will no longer be
building wheels for dependencies).
+ urllib2 doesn't exist in python 3 - import from urllib.request instead
+ for linux builds open docker process with universal_newlines; this
opens a pipe in 'text' mode using the default preferred encoding
Yannick Jadoul