Fixes invalid clink.arg.new_parser() behavior when flag with appended parser is provided
Merged pull request #227.
Updated installer's URLs.
Added table of available hotkeys

Also formatted with [markdownfmt](https://github.com/shurcooL/markdownfmt), which may have moved some other things around a tad (but not in a way that will affect the rendered Markdown).
Merged pull request #236.
Moved vim modeline to the bottom of the file.
Consolidated digit-argument hotkeys.
Added link to Readline docs to explain function names.
Tabs vs spaces.
Fixed logic error.
Restore state after 'matches_are_files()' calls.
Consolidated redundancy.