Bump version to 3.1.0

This reverts commit b3e6a13e65.

README.md

@@ -18,13 +18,6 @@ This will prompt for a string and classify it, then print (in JSON) a dict of
 the format `{category: probability, category:probability, ...}` to stdout. (For
 information about `-n <max_ngram_length>`, see section "Ngrams.")
 
-Alternatively, if you only need the most likely category, you can use this:
-
-    gptc classify [-n <max_ngram_length>] <-c|--category> <compiled model file>
-
-This will prompt for a string and classify it, outputting the category on
-stdout (or "None" if it cannot determine anything).
-
 ### Checking individual words or ngrams
 
     gptc check <compiled model file> <token or ngram>