Fix bugs related to bottom kwarg in step histograms

Conflicts:

	lib/matplotlib/axes.py
	lib/matplotlib/tests/baseline_images/test_axes/hist_step.png
Consider ourselves interactive if sys.flags.interactive is set.
overloaded `_make_twin_axes` on `LocateableAxesBase` so that twinx and
twiny will work.
Add comment
add __eq__ to `matplotlib.gridspec.SubplotSpec`

This is to address the issue discovered in
http://stackoverflow.com/questions/20017314/how-are-existing-subplot-axes-retrieved-using-subplot2grid-gridspec-in-matplotli
where multiple calls to

   gs = gridspec.GridSpec(2, 1)
   ax1 = fig.add_subplot(gs[0, 0])
   ax2 = fig.add_subplot(gs[0, 0])

will return a new axes each time (unlike calls integers or tuples).
Added check to __eq__ to short-circuit out if the other object
does not have the necessary attributes.
added __hash__ so that data model will be happy again
Fix download button
Merge pull request #2409 from neggert/hist_bottom_fix2

Fix bugs related to bottom kwarg in step histograms
improve docstring and add test fot to_rgb(<float>)

Even if the docstring was saing it, emphasis that to_rgb/to_rgba do not
accept float as input, but string representation of a float.

As one might be tempted to had float->gray conversion add failing test
in case the functionality is added.

Side fixes :
    change tuple([value]*3) to (value,)*3 for speed

In [18]: %timeit  tuple([0.4]*3)
1000000 loops, best of 3: 505 ns per loop

In [19]: %timeit  (0.4,)*3
10000000 loops, best of 3: 23.5 ns per loop

In [20]:  (0.4,)*3 == tuple([0.4]*3)
Out[20]: True

Closes gh-2609
qt4 subplottool is modal now + new layout
subplottool -> whats_new.rst
fix wrong backend name in whats_new
cleanup in subplottool + new style qt fix

Signed-off-by: Thomas Hisch <t.hisch@gmail.com>
BLD Fix build failure on Python 3.4b1 for Windows Windows

As of version 3.4b1 the official CPython distribution for Windows uses Tcl/Tk 8.6.
Merge pull request #2613 from cgohlke/patch-1

BLD Fix build failure on Python 3.4b1 for Windows
Refactor mechanism for saving files.
Move all print_ methods to their backends.
Manage default format-to-backend mappings in backend_bases.
print_figure() can now determine the backend for saving figures.
Remove print_ code duplication, add canonical FigureCanvas names.
Better documentation for print_figure refactoring.
Merge pull request #2588 from pwuertz/print_refactor

Refactor mechanism for saving files.
added failing test