Refactor the CLI, part 1

[fghaas]

Pretty comprehensive update to make the CLI more testable and extensible, and to generally be more in line with established precedent for Python CLIs:

• Rather than keep the entire CLI functionality in a script outside the package, create a cli.py module containing a CLI class.
• Add a wrapper for the CLI in __main__.py, so we can invoke it with python -m olxutils.
• Rather than hand-craft the wrapper script, let setup.py do it for us via entry_points and console_scripts.
• Add improved testing for all of the above.

I want to subsequently make another round of changes to the CLI, so that rather than invoking olx-new-run we can make it olx new-run, with an eye towards adding other subcommands besides new-run.

[codecov-io]

Codecov Report

Merging #26 into master will decrease coverage by 20%. The diff coverage is 66.66%.

@@             Coverage Diff             @@
##           master      #26       +/-   ##
===========================================
- Coverage   88.65%   68.65%   -20.01%     
===========================================
  Files           3        5        +2     
  Lines          97      252      +155     
===========================================
+ Hits           86      173       +87     
- Misses         11       79       +68

Impacted Files	Coverage Δ
tests/test_cli.py	100% <100%> (ø)	:arrow_up:
olxutils/cli.py	48.14% <48.14%> (ø)
olxutils/templates.py	40.9% <0%> (ø)

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update c34f8da...d3594de. Read the comment docs.

[fghaas]

Hah, interesting. :) Codecov complains that percent coverage is down, because cli.py was never picked up by coverage earlier. Bit silly...

[fghaas]

@arbrandes, do you mind if I give you a nudge on this one?