[record]: print read/write sectors per second
[server] draw IOPS and I/O throughput graphs for each devices
[record]: generate command arguments for perfmonger-record with RecordOption#make_command
[perfmonger.rb] remove comments
add class StatCommand and StatOption for 'perfmonger stat'
include canvasjs.js and bootstrap.js
[server]: escape device name such as dm-0 for JavaScript variable name
[server] draw CPU usage graph

close #5