cpp_build.corpus: Driver function for the C++ function.
In textreg: n-Gram Text Regression, aka Concise Comparative Summarization

Given a labeling and a corpus, create a corpus object for use in textreg. Generally you should use the buildCorpus method, not this method.

1	cpp_build.corpus(corpus, labeling, banned = c(), params)

`corpus`	A list of strings or a corpus from the `tm` package.
`labeling`	A vector of +1/-1 or TRUE/FALSE indicating which documents are considered relevant and which are baseline. The +1/-1 can contain 0 whcih means drop the document.
`banned`	List of words that should be dropped from consideration.
`params`	List of parameters to pass to the call.