add benchmarks to documentation

[Roger-luo]

This includes:

• an interactive plot (can be update dynamically) for single gates
• qcbm benchmark (close 9 qubit performance benchmark #43 )

fix #164

[codecov]

Codecov Report

Merging #196 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##           master   #196   +/-   ##
=====================================
  Coverage      20%    20%           
=====================================
  Files           2      2           
  Lines           5      5           
=====================================
  Hits            1      1           
  Misses          4      4

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[coveralls]

Pull Request Test Coverage Report for Build 1210

• 0 of 0 changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage remained the same at 0.0%

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Totals
Change from base Build 1201:	0.0%
Covered Lines:	0
Relevant Lines:	4

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💛 - Coveralls

[GiggleLiu]

Where are the images of benchmark results?

[Roger-luo]

It's online. You can click to comparing each different benchmark.

https://plot.ly/~rogerluo.rl18/1

[Roger-luo]

good to merge? @GiggleLiu