Django-gapc-storage

- Fix 'ImportError: file_cache is unavailable when using oauth2client >= 4.0.0 or google-auth'
warning by disabling cache_discovery
- Change dependency to google-api-python-client 1.11

Fixed
- Fix pin syntax in setup.py for `google-api-python-client`

Fixed
- Pin `google-api-python-client` version and explicitly require `oauth2client`

Fixed

* fix hyperlink to google-api-python-client in documentation
* fix `num_retries` attribute error ([17](https://github.com/eldarion/django-gapc-storage/pull/17))

Added

* configure [`num_retries`](https://github.com/eldarion/django-gapc-storage/blob/ce15daca2026357cea9011c8c4a838d4719c8abe/README.rstgapc_storagenum_retries)

Fixed

* documentation updated with correct spelling of settings

Fixed

* calling open on a closed file will reopen the file ([12](https://github.com/eldarion/django-gapc-storage/pull/12))