Updated python and numpy/scipy build scripts

Uses new download location for python runtimes.
Specifies default stack (cedar).
Fetches the binary of the appropriate python version (python 3.4
only).

Added tar for pip 1.5.6 and updated pip install script.

Fixed scipy tar filename
Updated paths for LIBRARY_PATH and LD_LIBRARY_PATH
Merge pull request #1 from tianyupu/squash-commits-again

Squash commits