less: use Bootstrap columns for changeset graph Using a fixed width doesn't make good use of the available space. On small screens the graph uses too much space, so the other columns can not be displayed. On big screens there'd be more space to display more parallel branches in the graph.

# requirements.txt file for use as "pip install -r requirements.txt" as a
# readthedocs compatible alternative to "pip install -e ." which is a working
# alternative to "setup.py develop" which doesn't work with Mercurial 3.7
.