add end to end tests for delimited text file reader/writer
enhanced file reader writer tests
Merge pull request #47 from lefthandmagic/delimitedtext_test

Add end to end tests for delimited text file reader/writer
Convert LogFilePath constructor to a create method

The previous constructor didn’t really fit in with the other constructors
and felt a bit misplaced. It’s now been converted to a static method,
#createFromPath, that does all the path parsing and then simply returns
a new LogFilePath object.
Make it possible to override log filenames

This is sort of a work in progress, and so far all existing code has
been ported to using `Partitions` objects rather than simple String
arrays. While I’m all for keeping it simple, using arrays all over the
place will make the code more complex than needed.
Add helper methods for formatting of `Partitions`
Refactor LogFilePath constructor
Move private method in LogFilePath
Always include offset as last filename component
Always include Kafka partition in filename
Add support for custom delimiters in log filenames
Stray delimiters