use %matplotlib in example notebooks

[minrk]

• removes any mention of %pylab in our examples
• adds --matplotlib command-line flag, mapping to the new
• adds Populated namespace message to %pylab output, at the request of @fperez.
• fix unicode bug in SVG, discovered during testing

closes #3680
closes #3684

[Carreau]

Want to share the 2 list maybe ?

[minrk]

done.

[Carreau]

did you removed examples/notebooks/Part 3 - Pylab and Matplotlib.ipynb on purpose ?

[minrk]

Renamed it, forgot to add the renamed notebook. Should be there now.

[Carreau]

had a quick read-through. LGTM.

[dpsanders]

OK, seems fine playing around.

You don't want to add just the list of import statements in the pylab docs?

By the way, why is the default inline backend PNG? SVG seems to me to be a much better choice.
(But maybe it's slower to render?)

[dpsanders]

I like the --no-import-all option.
In a way, it would be nice to make that the default, but in the end for interactive use it really is much more practical to import all the names.

[dpsanders]

What about mention of --pylab?
There still seem to be a few of those (if I did the branching right -- still not very secure on that).

[dpsanders]

The main problem is perhaps htmlnotebook.txt, which I am working on rewriting.
Should I do a pull request with the current version?

[minrk]

@dpsanders - it was getting re-wrapped because it was in an argument instead of the main description. It should be more to your taste now:

In [1]: %pylab?
%pylab [--no-import-all] [gui]

Load numpy and matplotlib to work interactively.

This function lets you activate pylab (matplotlib, numpy and
interactive support) at any point during an IPython session.

%pylab makes the following imports::

    import numpy
    import matplotlib
    from matplotlib import pylab, mlab, pyplot
    np = numpy
    plt = pyplot

    from IPython.display import display
    from IPython.core.pylabtools import figsize, getfigs

    from pylab import *
    from numpy import *

If you pass `--no-import-all`, the last to `*` imports will be excluded.

[dpsanders]

Excellent, thanks!
'to' -> 'two' in the last line

[minrk]

'to' -> 'two' in the last line

how embarrassing! force-pushed fix, to hide my shame from the git history :)

[dpsanders]

And finally what is the rationale for the pylabtools imports?

By the way, how do you get such nice syntax highlighting...?

[minrk]

And finally what is the rationale for the pylabtools imports?

Backward compatibility. I'm not changing how pylab behaves. I don't remember when or why they were added.

By the way, how do you get such nice syntax highlighting...?

GitHub takes care of that, I just pasted the docstring inside

```python
<paste here>
```

so it treats the whole thing as Python (note how it highlighted any in the body text).