Allow trurl to read from stdin using pipes.

[jacobmealey]

This adds the ability to use pipes to read from stdin. Note that this keeps the -f - style as is, but can be removed if folks want that.
Example usage:

$ echo "www.google.com" | trurl 
http://www.google.com/
$ cat someurls.txt | trurl --get "{scheme}"
https
https
git
http
ftp
$ (trurl -s query="foo=bar") < someurls.txt
https://curl.se/?foobar
https://docs.python.org/?foobar
git://github.com/curl/curl.git?foobar

fixes #275

[jacobmealey]

Okay, it took an embarrassingly long time to figure out why it was failing. turns out github runners do weird things with standard in, but made some more bugs visible. Anyway, it should be all good now.

[jacobmealey]

okay something is busted on the tests runners in a way im not sure how to reproduce locally (they run fine on both my mac and linux machines). I'm gonna close this PR and rethink how to do these tests.