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.
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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
added failing test
slight tweak to example, as discussed in #1451 to change `plt.draw()`
-> `plt.pause(.001)` to fake animations.
Merge pull request #2606 from mdboom/webagg/download

embedding_webagg example: Download button does not work
setupext: put pkg-config -I, -L, -l locations at the head of the list

The assumption here is that we want the pkg-config info to take
precedence, so its -I and -L output should be prepended, not
appended to the lists used to construct the compiler and linker
commands.  It is less clear whether the -l info also should
be prepended, as it is in the changeset; ideally, it wouldn't
matter, but for some compilers, it might.  If so, -l can
be handled separately from -I and -L.
fix typo in furmsubplottool

Signed-off-by: Thomas Hisch <t.hisch@gmail.com>
Merge remote-tracking branch 'upstream/v1.3.x'

Conflicts:
	lib/matplotlib/axes/_axes.py
BUG: correctly convert labelsize -> int

Do this by getting the size value back from the underlying text
object.