Add sanic as an entry point command

[ahopkins]

One thing that I have always thought missing was this:

$ sanic server.app --port=5000 --workers=4

Since we already have...

$ python -m sanic server.app --port=5000 --workers=4

... this PR just goes one step further to adding the entrypoint to run the Sanic server with the sanic command.

[codecov]

Codecov Report

Merging #1866 into master will increase coverage by 0.01%.
The diff coverage is 87.50%.

@@            Coverage Diff             @@
##           master    #1866      +/-   ##
==========================================
+ Coverage   94.79%   94.81%   +0.01%     
==========================================
  Files          24       24              
  Lines        2307     2314       +7     
  Branches      421      422       +1     
==========================================
+ Hits         2187     2194       +7     
  Misses         75       75              
  Partials       45       45              

Impacted Files	Coverage Δ
sanic/__main__.py	76.92% <87.50%> (+5.04%)	⬆️

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[yunstanford]

IMO, probably better to expose entry_points via "entry_points/console_scripts" in setup.py

[ashleysommer]

@yunstanford

probably better to expose entry_points via "entry_points/console_scripts" in setup.py

I might be wrong, but I believe that is what this PR provides.

[ahopkins]

Exactly.

[yunstanford]

ahh, sorry, didn't read that carefully.. just saw that

if __name__ == "__main__":
    main()

and thought differentlly.