Pin mo_future to <3

[mafrosis]

Version 3 of mo_future is incompatible:

Traceback (most recent call last):
  File "main.py", line 20, in <module>
    from moz_sql_parser import parse
  File "/usr/local/lib/python3.7/site-packages/moz_sql_parser/__init__.py", line 16, in <module>
    from mo_future import binary_type, items, number_types, text_type
ImportError: cannot import name 'text_type' from 'mo_future' (/usr/local/lib/python3.7/site-packages/mo_future/__init__.py)

[klahnakoski]

Yes, there is a mo-future compatibility problem. I thought I fixed it, but I will look again