Add file_polling_input
Add meminfo decoder for file polling input
Add initial diskstats decoder for file polling input
Remove unnecessary cjson import
Add lua cpuload decoder
rename meminfo to memstats
Add cpustats filter
Generalized cpustats filter a little.
Add memstats lua filter
Change label to local in cpustats and memstats filters
Initial diskstats filter.
Add TickerInterval to file_polling_input.

Used in diskstats.lua decoder.
diskstats filter: Use rate of change for num writes/reads

Added anomaly detection as well.
Test file_polling_input
Add license to file_polling_input
Document lua stat filters/decoders.
Document file_polling_input.
Fix bug causing cbuf to be recreated every interval
Fix decoder/filter gh review issues.
Change gomock to robs fork