Fix HeaderUtils to support ruby version on CentOS 7
Fix HeaderUtils to support ruby version on CentOS 7

Apparently, the ruby 2.0.0-p598 (CentOS 7 default) breaks with the code
we were using. This commit replace it with a different syntax that
should be reverted when CentOS 7 updates its ruby.

mezuro/prezento,mezuro/prezento,mezuro/prezento