Simplify IO handling

- Remove IOWrappers/IOChain #29
- Cleaned up specs
- Re-add gzip decoder #29
- Start handling encoding stuff #2
- Simplify Getline parser
Remove unused require for stringio
Add CSV parser #8
Rewrite Threatinator::Feed

- No longer use PropertyDefiner
- Ensure that it returns immutable values wherever possible.
Improve specs/unit tests
Add autoshun shunlist feed