Add a module to test the memory usage with large libaries

This is a convenience script to test the speed and memory usage of Jedi with large libraries.

Each library is preloaded by jedi, recording the time and memory consumed by each operation.

You can provide additional libraries via command line arguments.

Note: This requires the psutil library, available on PyPI.

The following are the outputs of runs just after deleting the Jedi cache and then running a second time.

```
Time (s) | Mem (MB) | Package
------------------------------
     0.1 |        1 | re
     6.3 |       35 | numpy
     2.1 |        9 | scipy.sparse
     7.0 |       46 | scipy.stats
     2.5 |        6 | decimal
     0.1 |        1 | PySide.QtGui
     2.3 |       13 | Tkinter
------------------------------
    20.6 |      111 | Total

Time (s) | Mem (MB) | Package
------------------------------
     0.0 |        2 | re
     1.2 |       28 | numpy
     0.4 |        7 | scipy.sparse
     1.4 |       37 | scipy.stats
     0.4 |        6 | decimal
     0.1 |        2 | PySide.QtGui
     0.5 |        9 | Tkinter
------------------------------
     4.1 |       91 | Total
```