v1.1.9

Note: this was originally intended to be releases as 1.1.8, but was mistakenly tagged as .1.1.8. Making a new release as 1.1.9, with changes from 1.1.7 noted below

What's Changed

• Fixes #478 by @cmungall in #77
• schemaview rdflib loader by @cmungall in #79
• Fix get_mapping_index method by @sierra-moxon in #71
• add inverse and is_mixin methods by @sierra-moxon in #78
• function to return schema elements by id_prefixes by @sierra-moxon in #36

Full Changelog: v1.1.7...v.1.1.8