Formatting of rg.1.md. Remove backticks from already indented code.
Add missing italic to some arguments, Replace -n by --line-number in
--pretty for better clarity. Add explicit example of `*.foo` instead of
`<glob>` in examples. Add vim information to --vimgrep.
In src/app.rs, also changed help text for pattern and regexp. Actually,
"multiple patterns may be given" was not true for the standalone
pattern.
4c78ca8b70