Py keras extension (#3468)

* Added support for building Theano with GPU support.  Added a package
for the libgpuarry libary needed for Theano.

* Added dependency on py-pexpect package which ipython requires.

var/spack/repos/builtin/packages/py-ipython/package.py

@@ -53,6 +53,7 @@ class PyIpython(PythonPackage):
     depends_on('py-prompt-toolkit@1.0.4:1.999', type=('build', 'run'))
     depends_on('py-traitlets@4.2:',             type=('build', 'run'))
     depends_on('py-decorator',                  type=('build', 'run'))
+    depends_on('py-pexpect',                    type=('build', 'run'))
 
     depends_on('py-appnope', type=('build', 'run'),
                     when=sys.platform == 'darwin' and