Adds changeOrigin flag to http-server proxy.

After some poking around in the ProxyServerAddon and adding back the `host` param as the third parameter in here:

    app.use(function(req, res) {
      return proxy.web(req, res);
    });

I started poking around in node-http-proxy and found some earlier issues related to the "Host" header. http-proxy does not seem to change the Host header for outgoing requests, so you have to flag `changeOrigin` to make this happen.

I added changeOrigin and this immediately fixes my bugs. So, I'm not sure if this is the correct implementation (perhaps this should be an option sent to the proxy via cmd line or a ./server proxy), but I figured I'd push it so you can see where I am at. Hope it helps.

References:

* [Use changeOrigin for proxyRequest](https://github.com/nodejitsu/node-http-proxy/commit/cee3e2f590058aa049b2f0b463e50e96272039f3)
* [Original host not being passed through](https://github.com/nodejitsu/node-http-proxy/issues/621)
* [Host header comments](https://github.com/nodejitsu/node-http-proxy/issues/150#issuecomment-2702793)
Doesn't parse proxy url
Test that proxying to subdomains uses the right host.
Merge pull request #2615 from typeoneerror/ember-cli-http-proxy-2596

Adds changeOrigin flag to http-server proxy.
Add #2615 to CHANGELOG.
make application instances not use Pascal case
Trim trailing whitespace
The generated meta tag is now self closing
Merge pull request #2661 from xymbol/trim-whitespace

Trim trailing whitespace
Trim trailing whitespace
Also updated the base tag (now self-closing)
Merge pull request #2662 from toranb/master

The generated meta tag is now self closing
Remove extra newlines inserted by addons that don't implement contentFor
Merge pull request #2664 from kanongil/remove-addon-newlines

Remove extra newlines inserted by addons that don't implement contentFor
Update CHANGELOG for 0.1.4.
Bump version to 0.1.4.
Ember CLI, PhantomJS in blueprint README prereqs

Adds Ember CLI and PhantomJS to the "prerequisites" section of the
README file generated by the default app blueprint.
Merge pull request #2666 from corpulentcoffee/readme-prereqs

Include Ember CLI and PhantomJS as "prerequisites" to the default app blueprint's README
Updating to new appveyor URL
[WIN] - Make all tests pass