fixed edge case where parsing loglines could break when they don't have datetime but do have duration.
made mlogvis much faster by checking logline parsing first for duration, then for datetime. Fixes #134.
first optimization, check for duration first, then datetime (only applies to --optime-start)
don't extract datetime of each line.
few minor changes to improve performance in certain edge cases.
small cosmetic change in code.
Merge branch 'mplotqueries-performance' into develop. Fixes #135.
added duration extraction for "flushing mmaps" log lines.
moved binary search to advance to a start date from datetime_filter to LogFile. It is more useful and useable from other components there.
added MaskFilter class. Takes another log file as mask and pads each event in that file. Only accepts log lines that lie within these masked areas. See #138.
extended MaskFilter to also support --mask-center as an argument. It can be 'start', 'end' or 'both'.
Added tests for mask filters.
Merge branch 'feature-138-masks' into develop. Fixes #138.
added filter masks to CHANGES.
changed the histogram plots to use "stacked" mode as default again. To disable, use `--no-stacked`. Fixes #141.
fixed a bug where 0ms durations (and other 0 values) are not plotted in mplotqueries. Fixes #144.
mongos start at the beginning of the port range now.

makes it easier to start a sharded cluster and connect straight to a mongos.
included mongos port range at beginning in CHANGES.
use absolute data paths to better identify the ps aux | grep mongo outputs. fixes #143.
sub-parsers added for start/stop/restart/list commands.
fixed a bug where the parsing of "flushing mmaps" durations wasn't working.