Deactivate tooltip on tab by default.

Codepath is **not** removed by this.
Update some example notebook with Shift-Tab
Remove tooltip on tab logic
Switch default IPython directory back to ~/.ipython

As discussed at the dev meeting, we care more about a consistent default
across platforms than half-heartedly following the XDG specs.
Update tests for IPython.utils.path
Update doc references to .config/ipython
protect against broken repr in lib.pretty
test bad repr
be really super ultra safe about reprs

don't trust exception strings or class attributes.

adds _safe_getattr, used in a few higher level places to protect against bad objects
test really bad repr
update man page to reflect XDG disrespect :)
remove XDG link
add note to "what's new"
a couple of more stray XDG / .config references
add missing pandoc declarations

Shaded environment and highlighting commands required for code in markdown cells

closes #4245
fix ansi coloring

scoping and command names were incorrect
use align environment, not aligned

aligned is only for when you are already inside a math environment (e.g. inside align)
test changes

- add markdown code block to test notebook
- update ansi filter test
Merge pull request #8 from ivanov/ipython-dir-default

main change is adding a what's new entry
Rework setup to allow installing on Python 2 and 3.

Scripts named ipython and ipython[23], etc.

Neither distutils nor setuptools made this easy.