Data.Fixed Missing E4, E5, etc

[Andrew Martin]

I've been working on a library for parsing geolite's GeoIP csv file
(http://hackage.haskell.org/package/geolite-csv-0.2/docs/Geolite-Types.html).
In this file, the latitude and longitude are always given to four
decimal points of precision. It seems like the Fixed data type (from
Data.Fixed in base) is the best choice for representing this.

However, the precision levels provided are:

- E0
- E1
- E2
- E3
- E6
- E9
- E12

I would like to propose adding all of the missing ones into Data.Fixed
as well. Even though needed a four-decimal-point-precision number is
uncommon, it's not unheard of. Admittedly, the precision offered by E11
seems unlikely to ever be needed, but I think it would be nice for
completeness. I would be happy to PR this if others agree that it's a
good idea.

-Andrew Martin