File options

Closes #11 

- Added some new options to handle file rotation. 
- Changed way files are named using timestamps. If you use auto generated file names via a time, the format is now "{timestamp}.extension" instead of using numbers. Mixing timestamps with sequencing numbers doesn't make sense.
- Added ability to filter timestamps via `filter` option.

:warning: not sure what I should do versioning here since technically the file naming format has changed.