Is --option=val format supported?

Hi.

Is `--option=val` options format supported?
I've did some testing and it doesn't seem to be supported. If I'm right, is there a reason why it's not supported? Can we have/add support for it?

Here's a diff of test that fails and proves my point:
```
diff --git a/test/integration.js b/test/integration.js
index 69a9018..086f9eb 100755
--- a/test/integration.js
+++ b/test/integration.js
@@ -414,7 +414,7 @@ describe('integration tests:', function () {
});

it('should use minimist\'s parse through the .types() method', function (done) {
- exec('typehappy --numberify 4 -s 5', done, function (err, data) {
+ exec('typehappy --numberify=4 -s=5', done, function (err, data) {
(err === undefined).should.be.true;
data.options.numberify.should.equal(4);
data.options.stringify.should.equal('5');
```

Thanks! :heart: