CONNT-25: Updated documentation:

- Marked Django 1.11.x as the only supported Django version.
- Updated some copyright notices.
- Updated installation and quick-start instructions for use with new
version of Django.
- Removed unneeded warning about pip version.
- Updated instructions to emphasize that 'crispy_forms' must be
included in list of installed applications.
- Added dedicated section for upgrade instructions. Covered some
general principles and upgrade from 0.3.x to 1.0.x.
- Updated release notes.
- Added information about Graphviz being the external dependency.

CONNT-28: Updates to documentation, requirements handling, and minor fixes:

- Fixed syntax error in MANIFEST.in file for recursive-exclude.
- Merged the about section from documentation into the README file.
Documentation now references README file instead of duplicating the
data. Minor formatting and wording fixes were made as well.
- Updated Sphinx configuration to use same string for both release and
version (deduplicate it a bit).
- Added a new, develoment-related, section to the documentation. Describes
how to set-up the development environment, as well as some maintenance
tasks.
- Updated quickstart instructions so they actually work. Switched to
using the pip install from PyPI instead of repository.
- Introduced pip-tools use for the development requirements file.
- Switched to using more fixed requirements in the setup.py.
- Removed test requirements from the setup.py.