Pannellum 2.5.3

Bugfixes:

• Fixed loading scenes after previous load failure
• Fixed regression that caused auto-rotation to stop after one revolution
• Fixed behavior of multiResMinHfov to match documentation;
  default multi-resolution minHfov behavior now matches pre-v2.5

Improvements:

• Added optional scale parameter to scale hot spots while zooming
• Improved recovery from failed scene loading

API improvements:

• Added optional pitch argument to startAutoRotate

Other:

• Added Journal of Open Source Software (JOSS) manuscript
• Numerous documentation improvements per JOSS review (thanks @vsoch and @Fil)
• Improved continuous integration and automated testing support
• Clarified generate.py error messages
• Added Dockerfile for generate.py