Fixes issue #9 by ensuring that idref/timestamp combos are valid, and by detecting all major elements that have IDs but lack timestamps
Add support for --recursive option. Fixes #35
Fix bad quote character
Merge pull request #43 from STIXProject/issue_35

Add support for --recursive option. Fixes #35
Merge pull request #42 from STIXProject/correct_timestamp_usage

Best Practice Validation of Timestamp Usage
Merged origin/master
Merged origin/master