Added get & put initial doc functionality, tests added
Added deleteInitialDocument with test
Added JSON serialisation/deserialisation to Diff and DiffOp, with tests
Removed superfluous helper class
Condensed down JSON serialisation tests
Removing excess type coercions
Merge pull request #17 from anchor/wip-diff-json

JSON serialisation/deserialisation for diffs
Merge pull request #16 from anchor/wip-initial-doc

Operations to store initial documents in database
Merge branch 'master' into wip-document-crud

Conflicts:
	src/Retcon/Diff.hs