Add string input

[tomron]

Add a flag or an option to do something similar to -

cat f | typo -s > new_file
typo -s <string> > new_file
use case -

1. Want to create a new file and not to override existing one
2. Get input from user and output it.

[intgr]

A streaming mode using stdin/stdout seems pretty useful.

[ssbarnea]

This would an essential feature that would enable us to also check the last commit message for spelling errors. Without it I am not sure how it would be possible to check last commit.