Match existing segmented LCM groups to those in incoming fit data

When you load a segmented LCM it has pre-existing segments. When
calling .fit() the incoming data may not have all those segments
(.e.g. the data has been changed since the last fit).
This removes an existing segments that are not in the incoming data.
PEP8 fix.
Remove non-existant segments from groups before fitting

A segmented model can have stored models for segments that are not in
incoming data. This clears any stored models that are not in the incoming
data.
Adding .name attributes to Segmented regression and lcm models.
Merge pull request #38 from synthicity/lcm-misc

Segmented* fixes