Fdstools

- First version of Stuttermark to be included in `fdstools`.
- Fixed crash that occurred when an empty allele (e.g., a primer dimer)
was encountered.
- Stuttermark now prints a warning if an allele is encountered that is
not a TSSV-style sequence.

- FDSTools will now display the help page if no command is given.
- The command-line help pages and debug output will now display a message
that FDSTools v2 is available and how to get it.
- When running setup.py on python3, a message is displayed that this
version is only compatible with python2 but a newer is available.
- Updated dependency requirements (python>=2.7.9,<3 and numpy<1.17).
- Includes [Samplevis v2.2.2](Samplevis-222)

- Changed the default value for -t/--min-r2 from 0.8 to 0.5. Stutter correction
based on a model with an r-squared score of 0.5 is usually better than no correction.
- Added the -C/--combine-strands option, to model stutter for the total number of
reads instead of fitting a separate stutter prediction model for either strand.
- Added the -T/--num-threads option (default: 1), which controls the number worker
threads to use when scanning for potential stutter events.
- Removed the random subsampling arguments.
- Flanks are now ignored even if the library file is given; repeats may
be interpreted as being slightly shorter if they continue into the flanks.
- Duplicate models are no longer produced for palindromic repeat units such as AT.

- Shut down cleanly when the output pipe is closed.

- Minor code change to fix warnings.

- Changed the default value of the -B/--bias-threshold option from 25 to 0.
- Changed the default value of the -Z/--allele-min-per-strand option from 1 to 0.
- Removed the -O/--online option.