Allow SPDY_INSTALL_SDK to be overridden

This change allows an external project to pass in a custom install script and configure so that the framework can be build as a subproject for debugging purposes
a few minor styling changes
Remove unrelated change to fix the build script
Merge pull request #62 from StanTwinB/develop

Allow SPDY_INSTALL_SDK to be overridden
Update project for Xcode 6