Merge pull request #27 from tumb1er/invalidation

Watch-free invalidation

Avoiding optimistic locking with WATCH in invalidation procedure in order to
exclude possibility of too much retiteration of transaction loop causing high
redis load.
Refactor and recomment invalidation procedure
Upped version to 0.9.4
Added test for #29.
Renamed ContribTests to IssueTests
Added tests for #30 and other cases with proxy models
Removed excessive newline
Change on base model now invalidates queries on its proxies and reverse.

Fixes #30
Upped version to 0.9.5
Added 0.9.5 changes
Added tests for multi-table inheritance #31
Added db file to .gitignore and clean up old virtualenv-in-. ignores
Postponed multi-table inheritance support
Said in README that expensive clone bug is django 1.4- only
Merge branch 'master' of github.com:Suor/django-cacheops
Handle connection failure in the case of invalidation
Reorganized the previous solution a bit, changed the name of the setting
Handle also a connection failure on schemes loading
Treat the simple cache utilization (trying to get from cache) as a cache miss if we cannot connect
Short-circuited the logic in `ensure_known` in case we fail to load schemes