Updated tox.ini for local testing.

I updated the tox.ini and tried to get all dependencies and to run as many of the test groups as possible. I also added a description how to install the dependencies for the javascript tests. This might need spelling and wording review.

I get all test groups but rpy2, which has a couple of failing tests. As this test group will be removed soon, this should not be an issue.

```
Tools and libraries available at test time:
   casperjs curses cython jinja2 jsonpointer jsonschema matplotlib mistune numpy pexpect phantomjs pygments pymongo qt requests slimerjs sphinx sqlite3 tornado zmq

Tools and libraries NOT available at test time:
   rpy2
```
> I think it makes sense to do a full test with tox. Partial tests can be used by invoking iptest after installing ipython.

I'm 50/50 both side can be defended. As we don't particularly use tox and this seem to help at least you, I'm fine withit.