Update reference documentation

Merge pull request NCATSTranslator#254 from cbizon/metaknowledgegraph

Specificity of /meta_knowledge_graph

Merge pull request NCATSTranslator#245 from NCATSTranslator/edeutsch-…

…valuetypeid-nullable

Make value_type_id nullable as intended

remove beta and ship it?

Bump version

Merge pull request NCATSTranslator#198 from NCATSTranslator/docs

Update/add documentation

Bump patch version

Merge pull request NCATSTranslator#194 from NCATSTranslator/fix-nulla…

…ble-$ref

Prepare for 1.0.0 final

Merge pull request NCATSTranslator#173 from NCATSTranslator/version-1…

….0.0-beta

Bump to version 1.0.0-beta

Merge pull request NCATSTranslator#84 from NCATS-Tangerine/edeutsch-p…

…atch-2

0.9.2