<package>/<package>.egg-info directories cause bad versions in requirements.txt

I usually install multiple packages under development in a virtualenv using `python setup.py develop`. As a result, I get a `.egg-info` directory (which contains `top_level.txt` etc.).

In presence of such packages, the `requirements.txt` file created by `pipreqs` contains entries like this:

mypackage.egg==info
otherpackage.egg==info

Instead, either the version from `setup.py` should be used, or maybe the version should be omitted altogether.

(see also #33 which was about checking local versions of packages)

Reproduce the issue by installing multiple packages with `python setup.py develop`, then run pipreqs and inspect the generated `requirements.txt`. Trace how `.egg-info` entries are interpreted; done when they no longer produce names such as `mypackage.egg==info`, with either the package version from `setup.py` or no version recorded.

Written by the indexing model from the issue text.