uplink 0.9.4 is no longer compatible with Python 2.7.5

[selimt]

Describe the bug
0.9.4 changed the way abc was imported from collections. See: #201
When Python 2.7.5 imports uplink we get the following error:

>>> import uplink
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python2.7/site-packages/uplink/__init__.py", line 4, in <module>
    from uplink import returns, types
  File "/usr/lib/python2.7/site-packages/uplink/returns.py", line 6, in <module>
    from uplink import decorators
  File "/usr/lib/python2.7/site-packages/uplink/decorators.py", line 6, in <module>
    from collections import abc
ImportError: cannot import name abc

To Reproduce

pip install uplink --upgrade
python
>>> import uplink

Expected behavior
We should be able to use uplink with Python 2.7 since it is still advertised as Python 2.7 compatible.

Additional context
I have not had a chance to test this to see if this issue is solved in future Python 2.7 releases but Python 2.7.5 is what we currently use.

[tirkarthi]

Seems 2.7 and 3.4 testing have been removed : #199

[Imaclean74]

Is it better to just deprecate 2.x support at this point ?

[prkumar]

I would prefer deprecating 2.x support at this point, considering we are over a year since 2.7 EOL. As more of our dependencies deprecate 2.7, supporting it will become more and more difficult.

@selimt - are you still using 2.7?

[selimt]

@prkumar Yes, we are in the process of upgrading all our code to Python 3.7 but currently we still depend on 2.7. If supporting 2.7 is no longer feasible we'll pin our requirement for 2.7 to uplink 0.9.3.
Thanks.

[prkumar]

I've merged #223 to add back 2.7 support in the upcoming patch release (i.e., v0.9.5). I'm thinking we should completely remove 2.7 support in the next minor version release (i.e., v0.10.0). I'll add some disclaimer to the README that instructs py27 users to pin uplink to "<0.10.0".

Thanks @shadchin for #223.