Extended parser to support pyct commands

[jlstevens]

Addresses #109. It isn't obvious how to do the right thing here but this seems to me like the easiest way to splice together two external parsers. It does mean if you mistype 'serve', then it is the pyct parser that will complain.

[jbednar]

Looks great, thanks!

[codecov-io]

Codecov Report

Merging #176 into master will decrease coverage by 0.14%.
The diff coverage is 16.66%.

@@            Coverage Diff             @@
##           master     #176      +/-   ##
==========================================
- Coverage   90.07%   89.92%   -0.15%     
==========================================
  Files          30       30              
  Lines        4746     4755       +9     
==========================================
+ Hits         4275     4276       +1     
- Misses        471      479       +8

Impacted Files	Coverage Δ
setup.py	0% <ø> (ø)	⬆️
panel/cli.py	67.74% <16.66%> (-23.17%)	⬇️

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[philippjfr]

Is 'serve' the only bokeh command we are supporting?

[philippjfr]

I'll merge, I'm not sure if we should support any bokeh commands other than serve but we should at least decide deliberately.

[jbednar]

The commands currently offered by Bokeh are:

$ bokeh --help
usage: bin/bokeh [-h] [-v] {html,info,json,png,sampledata,secret,serve,static,svg} ...

positional arguments:
  {html,info,json,png,sampledata,secret,serve,static,svg}
                        Sub-commands
    html                Create standalone HTML files for one or more applications
    info                print information about Bokeh and Bokeh server configuration
    json                Create JSON files for one or more applications
    png                 Create standalone PNG files for one or more applications
    sampledata          Download the bokeh sample data sets
    secret              Create a Bokeh secret key for use with Bokeh server
    serve               Run a Bokeh server hosting one or more applications
    static              Serve bokehjs' static assets (JavaScript, CSS, images, fonts,
                        etc.)
    svg                 Create standalone SVG files for one or more applications

I'm happy to be corrected, but I don't think there is any use for info or sampledata; people can call bokeh directly for those. I don't personally know any use for json or static, but someone who knows more might. secret, html, png, and svg sound useful to me, and something potentially useful for panel to provide.