V0.3.1

Enhancements:

• Dynamically collapse navbar. (#75)
• Support unit conversion for individual observations. (#77)
• Support multiple y axis in user defined charts. (#78)
• Support data binding for current observations. (#88)
• Allow label overrides in weewx.conf. (#95)
  Fixes:
• Calculation of wind min and max. (#87)
• Add jasOptions.gen to install.py. (#89)
• Memory 'leak' due to Chetah processing of #include. (#96, #98)
  Internal:
• Move looping from Cheetah to javascript. (#85)