New Formula: Pymol

This includes the option "default-mono" which disables stereo graphics
by default when running pymol.

Note that the default install is a svn revision. This is because the tarball is very much broken
for OSX, and I was unable to fix it with patches. Therefore, I start with a slightly newer version that the available tarball.

I have a couple points that I am not certain about:

1. I am attempting to explicitly add options to dependencies, but this is probably only available in a dev version of homebrew. Based on mxcl/homebrew#14456 I expect this behavior to come about in 0.9.5 . If there is a better way, please let me know and I will update the formula. Also, you may want the python and tk options to be behind an option like `--with-external-gui` that just enforces these rules. Please let me know if you need that.
2. I have 2 computers that have serious problems when it comes to stereo graphics. I am not sure how well spread this problem is, but this is why I added the "default-mono" option. This option makes the user need to explicitly declare stereo `-S` if they want it. However, if almost no mac works in stereo, I think the option should be reversed and it should be "default-stereo" option. What do you think?
3. my `test` function is two fold
    * command-line pymol test `pymol -c` and
    * graphics benchmark test of pymol, which actually displays pymol during the test.
    Is this acceptable that the pymol gui shows up during test? If not, the last line can be removed from `test`

If you have any comments, please or needed revision let me know.