Reconsider using characters presentation for double values, so it can take use of gzip

[xihui]

gzip can compress repeated characters a lot.

Useful for large array.

Or directly send the binary data for gzip to compress? Not easy on client side to extract data?

Test gzip compression on line, see how much it can compress
http://i-tools.org/gzip

[xihui]

Add this function until WebSocket compression is widely supported