Corrections to module 01_02.

**Changes to module 01_01**

Changed figures to use IPython python interface instead of shortcode. Seems more clear.

**Corrections to module 01_02**

*1.* In cell 91, there is no need to use an array slice on u.

*2.* In cell 92, z_exact is not an input parameter and should not be listed in the docstring.

*3.* In cell 95, you reference a temporary variable, z, which I don't think you mean to. Cell should read:

```python
error_values = numpy.empty_like(dt_values)

for i, dt in enumerate(dt_values):
    ### call the function get_error() ###
    error_values[i] = get_error(z_values[i], dt)
```

Thanks!