Transform command-line arguments passed by anaconda project

[jlstevens]

This PR helps transform arguments that may be passed to the panel console script that would not be accepted by bokeh without transformation.

[jbednar]

Note that using --allow-websocket-origin in this way requires bokeh 0.12.7 or later, which anaconda-project itself can't do (as it is meant to work with any Bokeh version, even though it doesn't currently), but it should be ok here because Panel requires a later version of bokeh anyway.

[codecov-io]

Codecov Report

Merging #133 into master will increase coverage by 0.03%.
The diff coverage is 96%.

@@            Coverage Diff             @@
##           master     #133      +/-   ##
==========================================
+ Coverage   89.88%   89.92%   +0.03%     
==========================================
  Files          27       28       +1     
  Lines        4153     4178      +25     
==========================================
+ Hits         3733     3757      +24     
- Misses        420      421       +1

Impacted Files	Coverage Δ
panel/tests/test_cli.py	100% <100%> (ø)
panel/cli.py	90.9% <94.73%> (+24.24%)	⬆️

---

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 33ddbd6...3a339d1. Read the comment docs.