Updated TOU marking schemalocation
Update top-level constructs to enforce valid version properties
Update conversion methods not to automatically provide class-level version number when instance does not have version attribute set
Updated COATests to use valid version number
Updated version number error message to display input value
Merge pull request #204 from STIXProject/issue_173

Update top-level constructs to enforce valid version properties
Add initial implementation of docs for API coverage info
add overview
add docstrings
Fix a couple minor things
Group STIX extension docs by extension point, rather than as one alphabetically sorted group
Put 'STIX' in front for consistency
Try putting extensions in a single table, but with blank lines separating different extension groupings
Merge pull request #205 from STIXProject/profile_docs

Add initial implementation of docs for API coverage info
add docstrings
Get rid of sphinx-build warnings.

Apparently module-level dictionaries confuse Sphinx without additional documentation.
Fix a few doc formatting errors
Merge pull request #207 from STIXProject/doc-adds

Add docstrings for exploit_target
Fixed issue where incorrect namespace was being generated for YaraTestMechanismType. Fixes #210
Fixed bug where Incident class never called super() in to_obj()