Add support for files without extensions, also for files not named main.swift

[Danappelxx]

For example, if I were to create a file called main.swift and fill it with:

#!/usr/local/bin/apous
print("Hello, World!")

then executing the following:

$ chmod +x main.swift
$ ./main.swift

Would simply output

Hello, World!

However, if I were to rename it to just main, or main1.swift, it starts throwing errors:

$ ./main
<unknown>:0: error: no input files

$ ./main1.swift
Only a 'main.swift' file can be specified.

If I wanted to, for example, have a build script created through apous, calling the file main.swift would be sort of ridiculous, setup or install makes much more sense.

Just a few thoughts - I really like apous either way :+1: