Add support for a global config file to supply default answers to ahkpm init

[joshuacc]

In ~/.ahkpm/config.json.

{
    "defaultInclude": "main.ahk",
    "defaultAuthor": {
        "name": "Pseudo Dionysius",
        "email": "dionysius@athens.example.com",
        "url": "http://www.athens.example.com"
    },
    "defaultLicense": "MIT"
}