+ ruby-parse: add ability to read fragment from stdin

[jstanley0]

use - as the filename to read from stdin

this is useful when parsing multiple lines or code containing characters that would otherwise need to be escaped

[jstanley0]

another option is to read a fragment from stdin where we're currently printing "need something to parse" and exiting (line 180 in runner.rb); I am happy with either approach

[iliabylich]

So this change allows running echo "foo" | ruby-parse -, right?

[jstanley0]

exactly - or just ruby-parse - and then paste some ruby code, followed by Ctrl+D

[iliabylich]

Thanks! Let me know if you need a release.