Fixed issue #9, external file load of images

Rev. 2.09 - 2013-02-17
* Fixed: Github issue #9 Corrupt ePub file generated when image url's
contains extra parameters
* Fixed: Unable to load external images on some PHP installations due to
restrictions on file_get_contents (PHP_INI: "allow_url_fopen" = false)
* Fixed: determining image mime type not working when external files
could not be opened (see above restriction)