Removed 'setuptools' from install_requires to fix "pip install -t <some_target>" installations

I use "pip install -t packages -r requirements.txt" to install all the project's requirements into a subdirectory of the project for Google App Engine since it doesn't support adding anything to site-packages.  I then have a script at startup to add this packages directory to the sys.path.

"pip install -t" appears to uninstall distribute (from flask-sqlalchemy's setuptools requirement) and then install it in the packages folder, which breaks future installations in requirements.txt (I get an error about unable to import setuptools).

Removing the requirement from flask-sqlalchemy\setup.py fixes the install of my requirements.txt.  I checked the blame, and 'setuptools' was added 2010-06-05 to silence a warning when using zc.buildout.  I think fixing pip install -t is better than having a warning (I checked all the other requirements for my project, and no others include setuptools).  https://github.com/mitsuhiko/flask-sqlalchemy/commit/dbb7163bfafc73ca020487c73f17b646a710227e