"timestamp with timezone" column type is converted to plain "timestamp"

[tyler-laberge]

Specifying a column type of "timestamp with timezone" should create a column in redshift of the type "timestamptz". See supported datatypes

Instead, it looks like this is getting converted to a regular "timestamp" type in DateTimeTypeRedshift.java/TimestampTypeRedshift.java (I'm guessing redshift timezone support did not exist at the time)

I think we just need to remove these custom datatypes and it should work fine. I have tried this on a fork and as expected the column in redshift is given the type "timestamptz".

Created PR #12 with this change