Start implementing Reader for batches

This would allow us to more dynamically deal with formatting.

We could do a formatter for any sort of output we want.

Still working on the internals / interface though
Some refactoring for clarity
Refactor tests a bit
Move logline out to it's own file

Also, a convenience wrapper for len(line)
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New Formatting Changes
Handle splitting long lines

Also fixed up some naming
Naming is hard
Fill LogplexLineFormatter.Read's buffer as much as possible

Cut's down on the number of calls to read
Fill LogplexBatchFormatter.Read's buffer as much as possible
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Naming is hard
WIP
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rename some files and do some docs
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wire it up
skip these for now
Benchmarking and some improvements

LogplexLineFormatter benchmark
1072 B/op -> 1046 B/op
Some caching and stuff

From this:
BenchmarkLogplexLineFormatter 5000000      3326 ns/op    1046 B/op
14 allocs/op

To this:
BenchmarkLogplexLineFormatter10000000      2050 ns/op     852 B/op
6 allocs/op