Replaced uwsgi with gunicorn (reason: downloads were not reliable with uwsgi)

gunicorn is built by buildout and has one external dependency: libevent
there is a configuration file, gunicorn_settings.py.
Command to run gunicorn: bin/gunicorn -c gunicorn_settings.py wsgi:application
updated documentation with new dependencies
added ext dependency to travis.yml
updated gunicorn documentation and foreman scripts. scripts still require testing
another change to .foreman file was needed
improved install docs for gevent libs
download dataset button
changed layout of buttons
Merge pull request #293 from grischa/download_dataset_button

download dataset button
Merge pull request #292 from grischa/gunicorn

Gunicorn provides reliable downloads, uwsgi doesn't. This replaces uwsgi
removing left over debug code
rearranging Experiment.safe slightly for better grouping of experiment views
new experiment list pages mydata and publicdata
fixing layout issues with new buttons
removed "Authors" from front page list
git-added missing files
fixed command formatting
Merge pull request #299 from grischa/datafile-list-layout-fix

Datafile list layout fix
Merge pull request #300 from grischa/front-page-improvement

Front page improvement
Merge pull request #301 from grischa/better-experiment-list

Better experiment list