[setup.py] fix installation error by replacing the ez_setup.py

o old ez_setup.py downloads the outdated package ``distribute``
o included the ez_setup.py which belongs to the ``setuptools``
[setup.py] force setuptools version >= 3.3 during setup
[tools, scripts] No file output from plot_test.py
[mix_adapt] bugfix GaussianInference for 1D data

o add test cases for 1 for GaussianInference and VBMerge
[tools] plot_mixture: fail on error for 1D data