Support for plugins requiring olefile will not be loaded if it is not
installed. Allows library consumers to avoid installing this dependency
if they choose. Some library consumers have little interest in the
format support and would like to keep dependencies to a minimum.
- Remove relative calls to pip, python (assume virtualenv activated or otherwise "safe" global env)
- Full define development and documentation requirements in requirements.txt
``make test-dep`` installs documentation dependencies too, hopefully that's not too annoying.
This means development process for documentation and code can begin with:
virtualenv .
source bin/activate
pip install -r requirements.txt
