Added checksumming to local transport, movd checksumming commands to base transport class, added stub _run_command method for other classes to implement
Small cleanups from kev's review
generate_checksums added to task list
Merge pull request #79 from capomastro/generate-checksums

Generate checksums
Implement chained hardlinking for all items other than the first when archiving
an artifact.

This avoids duplicating files.
Merge pull request #78 from bigkevmcd/dont-duplicate-archived-items

Implement chained hardlinking for archived items