Test: load docs from JSON and diff them

This test currently fails as the `diff` function is not implemented.
Comments
Tests are now using Hspec
GHCi should load modules from src/ and tests/
Test loading JSON files
Move canned test values into helper module
Helper to fail tests (via error) when unable to load doc
Add configuration for HLint
Generate key/value lists from documents
Update metadata in cabal file
Abandon diff op application to rework Document
Add custom Tree data type
Begin re-writing with rose tree based Document type
Fix some warnings
Working fromList and toList functions for Tree k v
Add (failing) tests for edge-labelled trees
Generate diff of two documents, via assoc lists
Merge remote-tracking branch 'origin/master' into wip-diffs
Revise details of Document type
Add a test make target so inotifymake.sh will work