Import IPython lazily

[methane]

import dotenv takes long time when IPython is installed.
This affects pypa/pipenv now. (ref)

This pull request imports dotenv.ipython lazily to avoid overhead.

[coveralls]

Coverage increased (+0.9%) to 86.224% when pulling 11dd923 on methane:lazy-ipython into 6eb1698 on theskumar:master.

[theskumar]

Thanks @methane for the PR, i'll include it after testing and add little documentation.

As far as pypa/pipenv is concerned, you may need to submit a separate PR to that repo, as it doesn't include this library directly but a copy of it: https://github.com/pypa/pipenv/tree/master/pipenv/patched/dotenv

Cheers,

[theskumar]

Oh. I see you already have PR open for it :)