[0.2.dev1] Fixes Small MNL simulation crash

[smmaurer]

This PR fixes a problem in the Small MNL template that was causing crashes in the simulation stage. This was identified by @xyzjayne.

Problem

Small MNL model steps were crashing in the simulation stage if the output column didn't exist yet, or in certain cases when multiple tables were being assembled.

Causes

When data was being assembled for simulation, the older TemplateStep._get_data() method was requesting the out_column because we used to update it locally before updating Orca (shared.py#L194). This caused errors when the column didn't exist yet.

It was also requesting the choice_column even when simulating, because of a coding mistake involving the special case of PyLogit model expressions (shared.py#L179), which i think was contributing to some of the crashes.

Solution

I updated the Small MNL template to use the new, cleaner utils.get_data() function for both estimation and simulation.

Testing

I replicated the crash in a unit test, and the changes resolve it. @xyzjayne reports that this branch fixes the crashes she was seeing as well.

Versioning

This PR increments the master branch to 0.2.dev1.

This seems like a pretty important bug fix, so i'm also going to apply these changes to the most recent production version and release it as v0.1.2 on pip and conda. (It will be at least a few weeks before v0.2 is ready for release.)

Before merging

• update changelog and version in docs

[coveralls]

Coverage increased (+1.9%) to 90.936% when pulling ab1af8b on small-mnl-bug into 1879a72 on master.

[mxndrwgrdnr]

Looks great. Much cleaner!