Fix building on OSX 10.9.1 (build 13B3116)
 * This was failing on my system due to a wrong output path, updated to work.
 * My uname -r: Darwin Redan 13.0.2 Darwin Kernel Version 13.0.2: Sun Sep 29 19:38:57 PDT 2013; root:xnu-2422.75.4~1/RELEASE_X86_64 x86_64
Add script to fetch dependencies before build.
 * Should work cross-platform, pure python code to download, verify hash, and extract tar.gz files
 * Tested on OS X 10.9.1