Use percona/go-mysql and go-test/test

* Faster, better, crash-proof query fingerprints
* [PCT-659](https://jira.percona.com/browse/PCT-659): One-line comments are not removed from fingerprints
* [PCT-380](https://jira.percona.com/browse/PCT-380): Numbers in table names are replaced with question marks
* [PCT-1021](https://jira.percona.com/browse/PCT-1021): SET statements in slow logs not parsed correctly
* [PCT-1022](https://jira.percona.com/browse/PCT-1022): Agent keeps logging warnings if InnoDB or user stats can't be collected
* [PCT-896](Query Analytics can produce very large data files): Query Analytics can produce very large data files
* Use [percona/go-mysql](https://github.com/percona/go-mysql) instead of [percona/mysql-log-parser]( https://github.com/percona/mysql-log-parser)
* Use [go-test/test](https://github.com/go-test/test) for `IsDeeply()` and `Dump()`
* Sort results to avoid false-positive failures
* Use `Class` consistently instead of `Classes` in one data struct
* qan.Worker detects mixed rate limits (and stops parsing); this was previously done in event aggregator
* Change RateLimit from `byte` to `uint` because valid value is 1-1000 according to [PS docs](http://www.percona.com/doc/percona-server/5.6/diagnostics/slow_extended.html#log_slow_rate_limit)