Implement gzip, gzip transfer encoding only for types which are not already gzipped (or very close to it)

[boutell]

gzip does not improve performance for PNG and probably would improve it negligibly for JPEG or GIF. There may be others but the important thing is to get started on recognizing these cases and eliminating the overhead in the azure storage layer in these cases. I would envision a file similar to contentTypes.js that maps which content types are precompressed and thus bad candidates for this approach.

[boutell]

This is not a blocker for release.