Ref-Time Support

- Initial support in metadata for the X-Ref-Time field by storing the current UNIX Epoch when the ref data changes
Bug Fixes

- Fixed MongoDB driver so that it passes unchanged
- Fixed Cassandra Mocking so that it passes unchanged
Bug Fix

- Cassandra needs to initialize the reftime by inserting it without changing the refcounts
Enhancement - Test Cleanup

- Update sqlite driver tests to use self.assert*
Pep8 Compliance
Bug Fixes

- Forgot the NotImplementedError for the abstract version
- Added test when the block doesn't exist to exercise the exception handling
X-Ref-Modified Header

- Update Block Model to easily get its last reference modified time
- Update Block Controller to return the last reference modified as X-Ref-Modified when retrieving a single block
Check x-ref-modified in Get Block
Merge branch 'master' into get_block_xrefmodified
Cassandra Fix

- Missed updating the Cassandra Scheme file
- Per Jamie, Cassandra won't allow reftime in the same table as the ref counter so we follow the model in Sqlite and put it in the blocks table
Merge branch 'master' into enhancement_ref_modified

Conflicts:
	deuce/tests/test_sqlite_storage_driver.py
Merge branch 'master' into enhancement_ref_modified
Sqlite Schema Version

- Schema is still version 1
- Tried to add the change as a new schema addition but setting a default value of "NOT NULL" or using strftime/strptime causes problems in the alter table functionality.
Merge branch 'master' into enhancement_ref_modified

Conflicts:
	deuce/model/block.py
	deuce/transport/wsgi/v1_0/blocks.py
Merge branch 'master' into get_block_xrefmodified
fix: cassandra config.ini

-  the db_module for cassandra should be 'cassandra' and not
   'cassandra.cluster', since thats being imported in cassandra metadata
   driver

-  cluster is configured as a list now, instead of a string.
Merge pull request #163 from TheSriram/cassandra_config

fix: cassandra config.ini
fix: cassandra metadata driver blocksize

Cast blocksize to integer.
The reference driver of sqlite has the same implementation.
fix: transport errors while using markers, offset

These errors were brought into the picture, when testing with the
cassandra metadata driver.

- The offsets were being cast to int, but not being explicitly passed down
  to the metadata layer.
- Falcon sets the return of req.get_param() to None automatically, if the
  param is not present.
Merge pull request #132 from BenjamenMeyer/enhancement_ref_modified

Enhancement X-Ref-Modified