Implemented c_code for AdvancedSubtensor1

Issue #783: python3 compatible - merge

Add dtype arg to zeros_like method of tensor vars

Conflicts:
	theano/tensor/elemwise.py

Minor stuff

More stable reduce operations by default

Fix check that was too restrictive

Update installation instructions for Anaconda

Checks the dimensions and bcast in inc_subtensor

 - Included six.py by Benjamin Peterson.  (Commit 62d8be3 2013-01-13.)
   See <https://bitbucket.org/gutworth/six>.

 - Moved Python 3 compatibility code to theano.compat.

Python 3 port now passes default "theano-nose" tests under pythobn 3.2.

Make sure min <= max in test_clip

Do not create a complex tensor with zeros, then cast it into floatX,
create the floatX zeros directly

If acc_dtype == output.dtype, nothing changes.

This dtype is to be used as accumulator, instead of self.dtype as was
previously the case. Then, the result is cast to self.dtype if needed.

Also implement the perform version using it.

Test default blas flags before using them