added --fast option

This is opposite --slow, filtering queries that took longer
than N millisecs.
update README usage
added default value fastms=1000ms to FastFilter similar to SlowFilter.
fixed bug where outputs of the form time=1ms were mistakenly treaded as durations at the end of the line, which caused errors.
resolved merge conflict.
[mlaunch] Print host and ports of launched replica set nodes
[mlaunch] Check if the port where the mongos/d is launching is available
refactored all tools to derive from either BaseCmdLineTool or LogLineTool. Added -v/--version flag.
added "dev" to version.
Merge branch 'base_tool' into develop
[mlaunch] Fix check_port_availability
had to remove -v for version because mlaunch can now take any additional parameters, like -vvv and pass it on to the mongod/s instances.
mlaunch can now take any additional arguments (like -vvv) and pass it on to the mongod/s instances.
added latest change for mlaunch.
Allow mlaunch to start multiple mongos with --mongos NUM. default is 1.

This fixes issue #30.
cleaned up CHANGES file. bug fixes (with issue numbers) first, then new features, minor bugs without issues.
limited the list of arguments that can be passed on to mongos.
This closes #31.
forgot to remove print statements.
Added Contributing page as tutorial.
changed some wording in contributing instructions. Added rule about commit messages.