update str checks to use basestring so unicode is valid
update str checks to use basestring so unicode is valid

tdhopper/pyLDAvis,bloody76/pyLDAvis,napsternxg/pyLDAvis,codingafuture/pyLDAvis,tdhopper/pyLDAvis,codingafuture/pyLDAvis,bloody76/pyLDAvis,bmabey/pyLDAvis,bloody76/pyLDAvis,kcompher/pyLDAvis,bmabey/pyLDAvis,bmabey/pyLDAvis,kcompher/pyLDAvis,napsternxg/pyLDAvis,codingafuture/pyLDAvis,tdhopper/pyLDAvis,napsternxg/pyLDAvis,kcompher/pyLDAvis