Fix: Do not use the non-public parse_requirements

[foosel]

pip.req.parse_requirements is not considered part of the public pip API by the pip developers and hence should never be used as such. Its signature can change at any given moment, making installations depending on it just break.

This patch moves the actual requirement specification over into setup.py and modifies requirements.txt to only contain a reference to the local package, in compliance with the suggested usage pattern for setup.py vs requirements.txt.

See also:

• http://stackoverflow.com/a/22649833/2028598
• https://caremad.io/2013/07/setup-vs-requirement/

Solves #36

[Booli]

+1

[Salandora]

+1

[pauly7300]

+1

[imrahil]

+1