Merge pull request #1964 from deepchem/nightly_version

import sys

import time

from setuptools import setup, find_packages

if '--release' in sys.argv:

      if line.startswith('__version__'):

        g = {}

        exec(line, g)

        if project_name == "deepchem":

          return g['__version__']

        else:

          # nightly version string .devYearMonthDayHourMinute

          base = g['__version__']

          dev_version = ".dev" + time.strftime("%Y%m%d%H%M%S")

          return base + dev_version

    raise ValueError('`__version__` not defined in `deepchem/__init__.py`')