Enhance tests environment on Travis CI build

[peter279k]

To let Travis CI build environment be similar with production environment, I plan to drop PHP built-in web server. And using the Apache+PHP environment instead.

@izniburak, once this issue is accepted, I will work on this.

[izniburak]

Hi @peter279k , this is great! It will be good. I think we can do it.

[peter279k]

Closed via PR #21.