Clean Makefile and add pip install of required pkg

Try to pip install packages that are need for each target.
Added pep8 commands to Makefile
Added unit test for PEP8 compliance

The goal is to get this test passing.
Removed old test files for harvester script
test dir passes pep8 check
setup.py passes pep8
Added install instructions to README
Removed tesseroid parallel recipe. Took too long
Cookbook passes PEP8
Better test msg for PEP8 check
fatiando package conforms to PEP8 standars
Added the requirements file
Don't tell people to e-mail me anymore
Changelog entry for PEP8 compliance
Tell Travis to install pep8
Fixed cookbook recipes and got rid of useless ones
Merge pull request #115 from leouieda/pep8

PEP8 compliance
Merge branch 'master' into prism-around

Conflicts:
	fatiando/gravmag/_prism_numpy.py
	test/test_gravmag_prism.py