Adds sendSignal and emit('message') with tolerances and expected values.

[tcr]

We had a very hard time explaining the utility of sendRawSignal and parsing raw message values. Also, IR tolerances are generally +/- 10% for most devices. Solve this using a simple API:

ir.sendSignal([8400, -4400, 640, -320, 1000])

And to parse

ir.tolerance = 0.1 // 10%
ir.expected = [8400, -4400, 640, -320, 1000];
ir.on('message', function (data) {
// packet received where all values were within tolerance of some value in expected
// `data` is an array of values from expected
});

Messages that have values not within tolerance are rejected and not emitted by message.

[johnnyman727]

Looks good but can you add relevant tests?