[#1149] Move minimum requirements into requirements.in and generate a
requirements.txt file from it using pip freeze

Conflicts:

	dev-requirements.txt
[#1149] Upgrade to latest nosetests
[#1149] Fix some pep8 issues and problems with pip requirements on travis
[#1149] Regenerate requirements file with older version of Babel and jinja2 that do not cause errors
[#1149] Pin requirements in minimum requirements file as discussed