Add support for arguments (like diff files, or files to compare) #41

I wish diffnav could read diff file as an argument.

Proposal 1

$ diff -u a.txt b.txt > patch.diff

$ diffnav -f patch.diff

Proposal 2

$ diffnav a.txt b.txt

# or,

$ diffnav -r a_directory b_directory

Proposal 3

Both Proposal 1 and Proposal 2 combined.

Advantages

• Less typings when using with diff.
• Easier debugging with debuggers like delve.
  • Please enlighten me if there is a better way to debug diffnav.