Publish documentation for old versions

Currently the docs reflect the latest release of JSHint. It would be great if the website could also expose information on prior releases because this recently-suggested approach (though value) is far from ideal:

You can browse to the version of which you are looking for documentation (v2.8.0) and read the comments in src/options.js

Because we are generating documentation from the source code, the ideal solution (as I see it) will require a fair amount of work. Pseudocode:

for each tag of the source code
  look up a version-specific source code parsing function
  apply that function to the code
  expand the documentation template with the parsed variables
update documentation pages to list all available versions

Start by reviewing how the website currently generates documentation from the source code, including the version-specific information in src/options.js and the available source tags. Done means exposing documentation for prior releases and updating the documentation pages to list all available versions.