Allow for 1 topic

[juniperlsimonis]

The math of the LDA inherently allows for as few as 1 topic.

1 topic is an important boundary situation that we want to be able to include in our models.

Unfortunately, the current LDA application via LDA() in topicmodels package doesn't allow for a single topic. It's not a simple fix in the R code, we'll need to dive into this more deeply.

[juniperlsimonis]

this should be accomplishable with the multi-LDA_TS functionality concept #149 and specifically #146 we can build simple "identity" and "identity but with error" models that are functionally 1-topic LDAs