iOS cracking scripts
If you're not using it for piracy (I assume you're maybe trying to access class method names to make a jailbreak tweak?) use dumpdecrypted. 

It allows you to decrypt a code-signed application, but due to the decryption method it wont allow the binary to run on iOS.

All decryption is handled on the device (you perform it over SSH by copying the dylib and running the binary), which means the app you wish to decrypt must also be installed to your device (or extracted and copied to /var/mobile/Applications or wherever iOS 8 changed it to)