validateTopic: Create validation tasks for topic model selection
In Luwei-Ying/validateIt: Validating Topic Coherence and Topic Labels

Create validation tasks for topic model selection

1	validateTopic(type, n, text = NULL, vocab, beta, theta = NULL, thres = 20)

`type`	Task structures to be specified. Must be one of "WI" (word intrusion), "T8WSI" (top 8 word set intrusion), and "R4WSI" (random 4 word set intrusion).
`n`	The number of desired tasks
`text`	The pool of documents to be shown to the Mturk workers
`vocab`	A character vector specifying the words in the corpus. Usually, it can be found in topic model output.
`beta`	A matrix of word probabilities for each topic. Each row represents a topic and each column represents a word. Note this should not be in the logged form.
`theta`	A matrix of topic proportions. Each row represents a document and each clums represents a topic. Must be specified if task = "T8WSI" or "R4WSI".
`thres`	the threshold to draw words from, default to top 50 words.