Incompatibility with tm 6.0

Hello, there was a incompatibility issue with tm 6.0 which behaved differently from tm 5.2, leading to an error message "Error in inherits(doc, "TextDocument")". It can be fixed by converting the character string to TextDocuments before DocumentTermMatrix is called. Borrowed the solution fromhttp://stackoverflow.com/questions/24191728/documenttermmatrix-error-on-corpus-argument