Update Server.hx

Fix compilation errors.

```bash
grunt server
Running "server" task
>> The `server` task has been deprecated. Use `grunt serve` to start a server.

Running "serve" task

Running "clean:server" (clean) task

Running "haxe:all" (haxe) task

Building Haxe project... 
build.hxml
haxe/Server.hx:19: characters 15-16 : String should be js.support.RegExp
haxe/Server.hx:19: characters 15-16 : For function argument 'path'
haxe/Server.hx:30: lines 30-33 : req : Unknown<0> -> res : { status : Int -> Unknown<2>, sendfile : String -> Unknown<1> } -> _ : Unknown<3> -> Void should be Dynamic -> js.npm.express.Request -> js.npm.express.Response -> js.support.Callback<Void> -> Void
haxe/Server.hx:30: lines 30-33 : For function argument 'errorHandler'
Fatal error: Error


Execution Time (2014-06-15 17:28:54 UTC)
server          2ms  ▇ 1%
clean:server    2ms  ▇ 1%
haxe:all      131ms  ▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇▇ 96%
Total 137ms
```