Added support for task arguments

[stevenvachon]

This is waiting on #46

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This change is 

[M-Zuber]

Overall this looks good, but I found the following edge cases that would still need to work:

• npm run watch should simply run all tasks defined
• npm run watch -- ...args should run all tasks defined passing in the args to each one

here is the setup I was using to test it package.json:

{
    "name": "npm-watch test",
    "version": "1",
    "devDependencies": {
        "npm-watch": "file:path to local version of npm-watch"
    },
    "scripts": {
        "watch": "npm-watch",
        "echo": "node index.js",
        "echo2": "node foo.js"
    },
    "watch": {
        "echo": "index.js",
        "echo2": "foo.js"
    }
}

index.js

function foo(arg) {
    console.log(arguments);
}
foo(process.argv.slice(2));

foo.js

function foo(arg) {
    console.log(arguments);
}
foo(process.argv.slice(2).reverse());

[stevenvachon]

We should add a test suite.

[M-Zuber]

We should add a test suite.

That is something I would love to do, if you have an idea on how to implement, please open an issue/pr so we can discuss it in a dedicated location

[stevenvachon]

I'd like to do it here in a separate commit, as it'll help me be sure that my PR passes your above case.

[M-Zuber]

Generally I would prefer to separate something like that out to a dedicated PR, but as long as each commit is self contained, go ahead and do it on this PR

[M-Zuber]

Travis and AV are both connected now