Dockerfile: Add php5-acpu package

The php5-acpu package should speed up page loading according to
phabricator documentation.

https://github.com/yesnault/docker-phabricator/issues/16
Codestyle: Spacing corrections

This removes
* Trailing whitespaces
* Trailing double-newlines before EOF
Merge pull request #18 from sils1297/pr/apc

Pr/apc