Ont-fast5-api

Added
- Useful error message if no input files found
Fixed
- filename_mapping output gave incorrect filenames

Added
- Script for extracting reads by id from `multi_read` files

Fixed
- Bug in output to `filename_mapping.txt`

Added
- Multi-threading support for multi<->single conversion for improved performance

Fixed
- Removed incorrect license accidentally added to README

Changed
- Minor documentation updates
- Follow symlinks when finding files recursively

Added
- Generic single- and multi- read interface via `get_fast5_file`

Fixed
- Incorrect time estimates for single-multi conversion
- Fixed path creation if not exist