Platform check accounts for Cygwin as well.
Merge pull request #7 from cadnano/shawn

Add slice view arrows for staple strands
Merge pull request #6 from sinverso/master

Changed platform check to accounts for Cygwin.
fix venv instruction
Add M13KO7 sequence
fixed addseqtool PyQt5-->5 native python string conversion issues and did style changes there too
truncated scale factor on zoom in status bar to 2 sig figs
Merge branch 'master' into shawn