Allow running tests programmatically

[ps-george]

Fixes #222

• Added main code into a function called run_locust that takes OptionParser object and additional arguments.
• Moved parser code into a file called parser.py
• Added tests to test_main.py for new changes.
• Added example file to demonstrate new functionality
• Added new docs for running locust programmatically
• Changed from gevent import wsgi in test_web.py to from gevent import pywsgi because it was throwing an error (also all uses of wsgi to pywsgi)
• Added Napoleon to Sphinx conf.py for sane parsing of function docstrings.
• Added functions is_taskset and load_tasksetfile since would be useful and minimal effort to add.
• Added create_options function to create default options for new mode

[codecov]

Codecov Report

Merging #799 into master will increase coverage by 0.25%.
The diff coverage is 76.85%.

@@            Coverage Diff            @@
##           master    #799      +/-   ##
=========================================
+ Coverage   67.44%   67.7%   +0.25%     
=========================================
  Files          15      15              
  Lines        1588    1483     -105     
  Branches      243     234       -9     
=========================================
- Hits         1071    1004      -67     
+ Misses        456     410      -46     
- Partials       61      69       +8

Impacted Files	Coverage Δ
locust/parser.py	100% <100%> (ø)
locust/main.py	30.33% <50.87%> (+4.16%)	⬆️
locust/contrib/fasthttp.py
locust/log.py	84.37% <0%> (+18.75%)	⬆️

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[ps-george]

Changed from gevent import wsgi in test_web.py to from gevent import pywsgi because it was throwing an error (also all uses of wsgi to pywsgi)

Note that before this change all Travis builds are failing (see https://travis-ci.org/locustio/locust/jobs/380659365)

[ps-george]

Open to any alternative suggestions to dealing with Travis CI no longer supporting python3.3 other than removing it from tox.ini and .travis.yml if anyone has any ideas.

[tysonclugg]

https://www.python.org/dev/peps/pep-0398/#lifespan

As of 2017-09-29, Python 3.3.x reached end-of-life status.

I'd drop support for 3.3.

[tysonclugg]

I've had a look through the changes, and I can't see any issues. Especially since the tests pass on this branch, and tests fail on master.

[cgoldberg]

I think dropping 3.3 support is fine, but not in this PR.. please propose that separately. also... all of the other changes unrelated to this PR (whitespace, refactoring, rearranging, doc theming, etc) really need to be moved into individual PR's.

[ps-george]

Okay, will do, it was just difficult to submit a PR that failed the CI.

Am on holiday for the next few days so next week some time. In the meantime if anyone else wants to raise PRs for some of the individual changes here feel free.

[cgoldberg]

it was just difficult to submit a PR that failed the CI

you can add your PR to fix CI first