Polish README.md

[SeanBryan51]

• Replace 'CABLE benchmarking' with benchcab
• Update description of package. E.g. benchcab does not produce plots locally, it can run more than two branches, etc.
• Documentation link shouldn't link to 'latest'
• Add acknowledgements
• Add badges for documentation and conda package (see Add badges to README #108)

Fixes #133

[codecov]

Codecov Report

Merging #134 (44873fc) into master (093bedf) will not change coverage.
Report is 1 commits behind head on master.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master     #134   +/-   ##
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  Coverage   88.47%   88.47%           
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  Files          27       27           
  Lines        1527     1527           
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  Hits         1351     1351           
  Misses        176      176