Demo app nightly builds should have debug symbols for Tangram-es

[matteblair]

When I download new nightly builds of the app, I want to be be able to attach a debugger and profiler to assess bugs and performance without re-building and re-deloying the build from my own machine.

This will require 'debug' builds of the tangram ios framework as well: https://github.com/tangrams/tangram-es/issues/1253