Convert config loading to TOML, refactor appropriately

This PR refactors SimplePush to use TOML config loading, changes the existing portions to a new Application based init system, and config loading for each section similar to heka's.

A variety of Go idiom portions were also cleaned up, the logger was factored into an extensible logger with a uniform interface.

Fixes Issue #35.

Awaiting r+ from @jrconlin, @rafrombrc.
Agreed, many things need access to them all over, this refactor was to try and centralize how they get to it. Going the next step to dealing with it, cataloging what needs access to what specifically and making a cleaner API for App (along with an interface) is purposely left out as that would make this muuuuch larger than it already is.