First use-case specification made. Adjusted readme to match API.
Updated readme with refined API.
bugfix on test user object to catch correct exception.
Basic specifications and implementation in progress. Just before starting to use opencv and do real object detection.
Large update to specifications.

Changed file and directory structure for clarity.
Separated out tests for main class, visual blocks, and helpers.
Specified dynamically loading visual blocks as plugins.
Specified helper functions.
Implemented helpers
Implemented runtime loading of all visual block plugins.
Consolidated test helpers into one helper module.
Removed transparency from screenshot sample (a real screenshot wouldn't have transparency with PIL).
Updated PQUtility user to have two versions of the screenshot:
pil (for patching) and cv (for confirming Subvisual output)
First use case working. Can create a screenshot visual and retrieve it reliably.