OemGatewayEmoncmsBuffer: call time() out of loop (minor)
OemGatewayBuffer: round timestamp when buffering
OemGatewayEmoncmsBuffer: 60s timeout in urllib2.urlopen()

Prevents the program from being stuck if network goes down while sending.

See discussion here:
https://github.com/Jerome-github/oem_gateway/issues/6#issuecomment-27151766