FIX OverflowError in TweetTokenizer
FIX OverflowError in TweetTokenizer

In python 3.7, `chr()` can raise `OverflowError` when value >= 0x80000000 (or < -0x80000000). This is encountered in https://github.com/nltk/nltk/issues/2557
nltk/nltk,nltk/nltk,nltk/nltk