bump imagemagick version for builds
fix mirror URL so we can grab archived releases too when building PHP
Apache/2.4.10
enable mod_remoteip for Apache
ngx_http_realip_module for Nginx
Nginx/1.6.0
fix binary buildpack branch in README
disable HHVM on cedar-14 for now
fix PHP extensions not getting installed when using both HHVM and PHP
fix imagick builds using wrong version
clean up and simplify some error handling