Release 0.8.7

[DeviaVir]

Included:

• Prebuilt directory #122
• Copy the symlink content #126
• Added travis ci support for node 6 #129
• Support to use package.json description #133
• allow injection of environment variables via config file at runtime (#132) #136
• Set environment variables before requiring module #137
• Fix Publish parameter not working when updating existing function #138