Add Standards API base function
Fix for optional package_intents

Package Intents are optional in STIX, and the original code throws an
exception of the source document does not have this.  Rather than
checking the way it was done, look for the presence of the attribute
and if present, then do the same thing.
Changes based on mgoffin comments
Removed the Cruft and fixed the Campaign reference
Merge branch 'Updates-mgoffin-comment' into StixApi
Remove extra reference to the Reference parameter

Reference is not a parameter passed in on the api call. Forgot to
delete it when cleaning up.
Make Event working function
Fix to properly handle True or False passed

Correct the hack i had in requiring a string of True or False for the
make_event parameter.  Now it properly handles Ture or False in proper
python form.
Merge pull request #167 from sabade/StixApi

Add Standards API base function