drop support for Py2 and Py3.4

[Borda]

I am trying to address #420 (comment)
cc: @hugovk if you would be so kind (as always you have been) and may help me, check I missed 🐰

[hugovk]

These can be tidied up:

fire/__main__.py:64:   if sys.version_info.major == 3 and sys.version_info.minor < 5:
fire/__main__.py:72:   elif sys.version_info.major == 3:
fire/helptext.py:540:      if sys.version_info[0:2] >= (3, 3):
fire/helptext.py:540:      if sys.version_info[0:2] >= (3, 3):
fire/helptext_test.py:133:      sys.version_info[0:2] < (3, 5),
fire/helptext_test.py:150:      sys.version_info[0:2] < (3, 5),
fire/helptext_test.py:168:      sys.version_info[0:2] < (3, 5),
fire/helptext_test.py:186:      sys.version_info[0:2] < (3, 5),
fire/testutils.py:76:     if sys.version_info.major == 2:

universal = 1 can be removed:

setup.cfg:2:  universal = 1

[hugovk]

The six dependency can be replaced and removed.

Running pyupgrade **/**.py --py3-plus can help, and also upgrade a lot of other syntax.

https://github.com/asottile/pyupgrade

[hugovk]

This dependency can be removed and replaced with stdlib's unittest.mock.

[hugovk]

Why choose 3.5 as the lower bound? 3.8 is the lowest supported: https://devguide.python.org/versions/

[Borda]

Why choose 3.5 as the lower bound? 3.8 is the lowest supported: devguide.python.org/versions

O wpul;d do it too, but following setup.py which classifies support for 3.5, so we can do the additional bump in other/following PR if @dbieber agrees 🦩

[a-detiste]

The Great Six Cleanser are watching you https://wiki.debian.org/Python3-six-removal :-)