Use default timestamp type parser

[aheuermann]

I noticed that timestamps did not include milliseconds when retrieved from the db. I looked at changing the TIMESTAMP_FORMAT, but this method will receive two formats one with milliseconds yyyy-MM-dd HH:mm:ss.SSS and other times with microseconds yyyy-MM-dd HH:mm:ss.SSSSSS. The stringToTimeStamp falls back to seconds if the date isn't specific. I talked to Doug, and this was added in 2012 when I don't think there was a parser for this type in pg-types, which was part of pg at the time. It has since been added, so removing this uses the default parser in pg-types](https://github.com/brianc/node-pg-types/blob/f320a111e242716dde68f619fdef44969803f039/lib/textParsers.js#L166).

Going to run this against the c2fo tests to make sure everything passes.

[coveralls]

Coverage increased (+0.004%) to 88.924% when pulling 8eedcfd on use-default-timestamp-type-parser into 110cf7e on master.

[aheuermann]

Looks like c2fo is still on 2.0.0, so will need to cut a 2.1.0 release.

[jonstacks]

@aheuermann, I have an open branch for c2fo that bumps node from 5 -> 6 and patio from 2 -> 3 if it matters and this can wait a week or so.

[aheuermann]

@jonstacks that sounds good, we can release it with that.