allow for cairocffi imports

Backport from master to allow cairocffi as a drop-in replacement for pycairo.

Fix for #825
Merge pull request #924 from esc/fix_cairo_cffi_import_0.9.x

allow for cairocffi imports
updating the copyright notice on the RTD site
updating the dates and attribution of the Copyright in the LICENSE file
Merge pull request #927 from gwaldo/0.9.x

0.9.x backport - Updating Copyright in LICENSE and RTD site
Backport of PR #158 (URL shortener) to 0.9.x branch
Contains new icon from PR #922
Oops, forgot __init__.py
Merging with latest 0.9.x
Merge pull request #938 from deniszh/0.9.x_url_shortener

0.9.x url shortener
URL shortener was added to 0.9.13 release notes
Merge pull request #940 from deniszh/0.9.x_release_notes

URL shortener was added to 0.9.13 release notes
Backport of PR #589 to 0.9.x
Merge pull request #941 from deniszh/0.9.x_cache_config

Backport of PR #589 to 0.9.x
Fixing release notes after #941
Merge pull request #942 from deniszh/0.9.x_release_notes

Fixing release notes after #941
Backport cache invalidation fix (#487) to 0.9.x
Possible fix for #929 ?
Bah, forgot to move if
Merge pull request #945 from deniszh/0.9.x_cache_invalidation_fix

0.9.x cache invalidation fix
Fixing caching issue similar to #467 but for rendered graphs.
See https://github.com/graphite-project/graphite-web/pull/945#issuecomment-54818928
Merge pull request #948 from deniszh/0.9.x_rendered_cache_fix

Fixing caching issue similar to #467 but for rendered graphs.