Repl completion changes

Because I want to push a new release (finally!), I've had to deal with the current repl, which didn't behave the way I wanted it to behave.

After analyzing I realized that the current REPL completion (which falls back to Jedi if the std lib one doesn't work), is just not working very well, because the std lib version sucks and is not context sensitive. Therefore I just removed all that (sorry @tkf for the extra amount of work).

The second thing I changed is that you have to use `export PYTHONSTARTUP="$(python -m jedi repl)"` instead of `export PYTHONSTARTUP="$(python -m jedi)"`. I did this, because I'm not sure if I want the repl thing to take the whole `__main__.py` in the future (who knows what we're doing with it) and I definitely want to be backwards compatible.

Please complain if either of these changes are not good (IMHO at least the second one is questionable, because I could as well write a `jedi.utils` function instead of abusing the `__main__.py` file, but I decided to do it like this because a utils function would just be a lot longer).

There are still some things I need to change to change for the next release, like better magic method support (otherwise our repl completion would just really suck). Also the import completion doesn't work, yet.

~ Dave