Fix UnicodeEncodeError in help.py

[maxkrivich]

I don't know why but on MacOS when you execute this command python -m pipenv.help and redirect output stream to some another file, script fails with exception.

$ python -m pipenv.help > test.txt 
Traceback (most recent call last):
  File "/usr/local/Cellar/python@2/2.7.15/Frameworks/Python.framework/Versions/2.7/lib/python2.7/runpy.py", line 174, in _run_module_as_main
    "__main__", fname, loader, pkg_name)
  File "/usr/local/Cellar/python@2/2.7.15/Frameworks/Python.framework/Versions/2.7/lib/python2.7/runpy.py", line 72, in _run_code
    exec code in run_globals
  File "/Users/maxkrivich/Projects/pipenv/pipenv/help.py", line 89, in <module>
    main()
  File "/Users/maxkrivich/Projects/pipenv/pipenv/help.py", line 48, in main
    print(u'Pipenv–specific environment variables:')
UnicodeEncodeError: 'ascii' codec can't encode character u'\u2013' in position 6: ordinal not in range(128)

[techalchemy]

Thanks for the pr (again)

I wonder if this works on windows... will test when I get home

[maxkrivich]

@techalchemy I'm not sure what it is reproducible on windows. That module really very powerful and I just wanna to improve them.

[techalchemy]

Yeah just want to make sure that the explicit encoding doesn't break anything in the console, checking now

[techalchemy]

works ok for me, thanks for the fix!