Add install-dev-requirements.pip

[msabramo]

Fixes #366

Without

$ pip install -e .
Obtaining file:///Users/marca/dev/git-repos/warehouse
  Running setup.py (path:/Users/marca/dev/git-repos/warehouse/setup.py) egg_info for package from file:///Users/marca/dev/git-repos/warehouse
...
Downloading/unpacking pyramid>=1.6.dev0 (from warehouse==15.0.dev0)
  Could not find a version that satisfies the requirement pyramid>=1.6.dev0 (from warehouse==15.0.dev0) (from versions: 1.5.3, 1.5.2, 1.5.4, 1.0.1, 1.0.2, 1.0, 1.0a1, 1.0a10, 1.0a2, 1.0a3, 1.0a4, 1.0a5, 1.0a6, 1.0a7, 1.0a8, 1.0a9, 1.0b1, 1.0b2, 1.0b3, 1.1.1, 1.1.2, 1.1.3, 1.1, 1.1a1, 1.1a2, 1.1a3, 1.1a4, 1.1b1, 1.1b2, 1.1b3, 1.1b4, 1.2.1, 1.2.2, 1.2.3, 1.2.4, 1.2.5, 1.2.6, 1.2.7, 1.2, 1.2a1, 1.2a2, 1.2a3, 1.2a4, 1.2a5, 1.2a6, 1.2b1, 1.2b2, 1.2b3, 1.3.1, 1.3.2, 1.3.3, 1.3.4, 1.3, 1.3a1, 1.3a2, 1.3a3, 1.3a4, 1.3a5, 1.3a6, 1.3a7, 1.3a8, 1.3a9, 1.3b1, 1.3b2, 1.3b3, 1.4.1, 1.4.2, 1.4.3, 1.4.4, 1.4.5, 1.4.6, 1.4, 1.4a1, 1.4a2, 1.4a3, 1.4a4, 1.4b1, 1.4b2, 1.4b3, 1.5.1, 1.5.2, 1.5.3, 1.5.4, 1.5, 1.5a1, 1.5a2, 1.5a3, 1.5a4, 1.5b1)
Cleaning up...
No distributions matching the version for pyramid>=1.6.dev0 (from warehouse==15.0.dev0)
Storing debug log for failure in /Users/marca/.pip/pip.log

With

$ ./install-dev-requirements.pip
...
Successfully installed WebOb repoze.lru zope.interface zope.deprecation venusian translationstring PasteDeploy pyramid click gunicorn hiredis itsdangerous pyramid-jinja2 pyramid-services pyramid-tm readme setproctitle transaction tzf.pyramid-yml zope.sqlalchemy warehouse pymlconf
Cleaning up...

[dstufft]

This already exists at dev/requirements.txt.

[msabramo]

Oops, so it does. Somehow missed it.