Allow input from stdin

**Feature request**

Device logs don't always come directly from ADB. It would be nice to be able to pass in a previously-acquired log for formatting.

Example possible usage:

* taking input from stdin:
```
pidcat < ~/Desktop/logs/crash_dump.txt
```

* taking input as an argument:
```
pidcat -l ~/Desktop/logs/crash_dump.txt
```

Start at pidcat's command-line input handling and trace how log data currently comes from ADB. Support both stdin redirection and the proposed -l ~/Desktop/logs/crash_dump.txt argument, then verify that previously acquired logs are formatted as expected.

Written by the indexing model from the issue text.