Do not track binlogFilename/binlogPosition when GtidSet is set

[shyiko]

#250 (comment)

NOTE: having binlogFilename/binlogPosition avoids scanning unnecessary logs so check what are the options before blindly disabling binlogFilename/binlogPosition tracking.

[osheroff]

hey @shyiko this is actually pretty nasty / dangerous; see

zendesk/maxwell#1129 (comment)
and
zendesk/maxwell#1192

turns out that unless we jump through a lot of hoops to reconnect in GTID land, things go quite wrong.

[shyiko]

Fixed in 0.18.0.