dict: Include ourselves in dictionary
Remove '-r' recursive flag

If user specifies directory then it means user wants to check it
recursively.
Use 'check current directory' as common case

Checking current directory is something more widely used than
checking STDIN. Set is as common case.
Fix spell error using codespell tool
Install binary file as 'codespell' instead of 'codespell.py'

Users don't have to know that this tool is written in Python
Move dictionary name to optional parameter

Most often users just need the default dictionary, so let's create an option
with default value set to dictonary.txt. Users can overwrite this
parameter with its own dictionary.