Depend on Theano's master branch (not v0.6)

`as_op` was introduced after the 0.6 release of Theano (commit
c5b999ed).

See b26ac39 and #389 for an explanation of why '<=' is used instead of
'=='. As discussed in #389, this won't trigger a Theano update if the
user already has it installed, so previous Theano versions will have to
be removed first. Of course, this will only matter if the `as_op`
functionality is being used.

Fixes #613.

Author: kyleam

setup.py

@@ -27,12 +27,16 @@
                'Operating System :: OS Independent']
 
 install_reqs = ['numpy>=1.7.1', 'scipy>=0.12.0', 'matplotlib>=1.2.1',
-                'Theano==0.6.0']
+                'Theano<=0.7dev']
 
 test_reqs = ['nose']
 if sys.version_info[0] == 2:  # py3 has mock in stdlib
     test_reqs.append('mock')
 
+## The current release of Theano does not support `as_op` decorator, so
+## we're using the developmental version from github.
+dep_links = ['https://github.com/Theano/Theano/tarball/master#egg=Theano-0.7dev']
+
 if __name__ == "__main__":
     setup(name=DISTNAME,
           version=VERSION,
@@ -49,5 +53,6 @@
           package_data = {'pymc.examples': ['data/*']},
           classifiers=classifiers,
           install_requires=install_reqs,
+          dependency_links=dep_links,
           tests_require=test_reqs,
           test_suite='nose.collector')