Problems setting up on Heroku

I am trying to get the free version of UseResponse working on Heroku. I was able to get every installation check to pass except for a writable cache directory. I removed the "/cache" directory from the installation check script, which enabled me to complete installation, but now I get errors when I try to load the home page. The errors seem to point to the cache directory not existing or there being something wrong with it:

Got error 'PHP message: PHP Fatal error: Uncaught exception 'Zend_Cache_Exception' with message 'cache_dir must be a directory' in /app/library/Zend/Cache.php:209

Stack trace:

#0 /app/library/Zend/Cache/Backend/File.php(154): Zend_Cache::throwException('cache_dir must ...')

#1 /app/library/Zend/Cache/Backend/File.php(121): Zend_Cache_Backend_File->setCacheDir('/app/cache')

#2 /app/library/Zend/Cache.php(153): Zend_Cache_Backend_File->__construct(Array)

#3 /app/library/Zend/Cache.php(94): Zend_Cache::_makeBackend('File', Array, false, false)

#4 /app/library/Singular/Bootstrap.php(528): Zend_Cache::factory('Core', 'File', Array, Array, false, false, false)

#5 /app/library/Singular/Bootstrap.php(341): Singular_Bootstrap->initAutoloader(Object(Zend_Config))

#6 /app/library/Singular/Bootstrap.php(129): Singular_Bootstrap->executeResource('autoloader', Object(Zend_Config))

#7 /app/index.php(85): Singular_Bootstrap->__construct('development', Object(Zend_Config))

#8 {main}

thrown in /app

/library/Zend/Cache.php on line 209

Any ideas? Is there a quick way to just disable the caching? Heroku does not allow setting of permissions on directories in an application.

Appreciate the help, thanks for the great product.