Get things in shape finally:
* Move the Forward code into its own module.
* Separate out the excluded MX filtering magic.
* Write tons of tests for the MX filtering.
* Normalize every name used in a comparison.
* Use Data.Map and Data.Set for MX filtering.
* Update some documentation.
* Update the ghci file with new modules.
* Add the Forward module to the cabal file.
* Make sure no spurious newlines are output.
* Update the TODO.
- [DH] src/DNS.hs
- [DH] src/Forward.hs
- [DH] src/Main.hs
- [DH] src/Report.hs