Remove 0x2 bit from SETTINGS_FLOW_CONTROL_OPTIONS.

It controls the connection window, but there is already a mechanism for
that in WINDOW_UPDATE with stream 0 and the END_FLOW_CONTROL flag,
therefore it is redundant.
Merge pull request #89 from willchan/FLOW_CONTROL_OPTIONS

Remove 0x2 bit from SETTINGS_FLOW_CONTROL_OPTIONS.