Enable relative URLs for permalinks, intended to reduce HTTP data, allow better data portability, and so on.
Code reorganization.
Synthesis will only support PHP 5.0.0 at this point.

A more robust version check will be put in place later, as currently this only takes into account activating the theme normally (not the customizer or preview).

And while I want to encourage users to use up-to-date software (WordPress, PHP, or whatever else Synthesis may require), I don't want to be a dick about it, so more helpful notices will be put into place in time as well.
Further code cleanup of primary functions file.