Bug? SyntaxWarning: invalid escape sequence '\_'

[travis-leith]

Whenever I load stepmix, I get a complaint about [this line](SyntaxWarning: invalid escape sequence '_')

>>> from stepmix.stepmix import StepMix
C:\repos\stepmix_testing\.venv\Lib\site-packages\stepmix\stepmix.py:127: SyntaxWarning: invalid escape sequence '\_'
  Save the estimated parameters of all initializations to self.param_buffer\_.

[sachaMorin]

This is noisy but harmless. I'll try to fix it in the next release