Port one-liner scenario from line-number option cuke.

It should also work for appending to path.
Remove `--line-number` option.

CLI filtering options are meant to globally apply
but `--line-number` really only makes sense in the
context of a particular file.

rspec path/to/spec.rb:12:23 is a better way to
filter to an example based on the line.

Fixes #1243 and paves the way for #952.
Merge pull request #1415 from rspec/remove-line-number-filtering

Remove line number filtering