Finalize changelog for v1.36.5

Finalize changelog for v1.36.4

Finalize changelog for v1.36.3

Finalize changelog for v1.36.2

Finalize changelog for v1.36.1

Merge pull request AcademySoftwareFoundation#137 from materialx/dev_1.36

Merge branch 'dev_1.36' into master

Finalize changelog for MaterialX 1.35.5 (AcademySoftwareFoundation#103)

This changelist finalizes the changelog for MaterialX 1.35.5, and adds a link to the developer guide in the top-level readme.

Finalize changelog for MaterialX 1.35.4 (AcademySoftwareFoundation#54)

Finalize changelog for MaterialX 1.35.4

Also:
- Switch Appveyor from VS2017 to VS2015
- Add a type alias for string vectors

Merge pull request AcademySoftwareFoundation#33 from jstone-lucasfilm…

…/master

Update instructions for building API documentation

Merge pull request AcademySoftwareFoundation#7 from jstone-lucasfilm/…

…master

Document the OSL version for reference implementations