Added theano logos.

a36a1bfb · Joseph Turian · d09d53a9 · a36a1bfb · a36a1bfb · a36a1bfb
--- a/doc/images/snake_theta2.png
+++ b/doc/images/snake_theta2.png
--- a/doc/images/theano_bw_parens_transparent.png
+++ b/doc/images/theano_bw_parens_transparent.png
--- a/doc/images/theano_logo.png
+++ b/doc/images/theano_logo.png