Specify size_or_ary contains ints

[aaronayres35]

part of #785
As mentioned in the issue, we can resolve many test suite errors with celiagg by enforcing these be ints. Note that scale itself I think can be a float (e.g. the scale_ctm method expects floats as arguments), however, size_or_ary gets used as a _width and _height and is assumed to contain integers.

Note, with this change I now see 2 failures in the test suite: EDIT: I only see the one error mentioned on the issue:

======================================================================
FAIL: test_draw_border_simple (chaco.tests.test_border.DrawBorderTestCase)
Borders should have the correct height and width.
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/Users/aayres/Desktop/chaco/chaco/tests/test_border.py", line 52, in test_draw_border_simple
    self.assertRavelEqual(actual, desired)
  File "/Users/aayres/Desktop/chaco/chaco/tests/test_border.py", line 29, in assertRavelEqual
    alltrue(ravel(x) == ravel(y)), "\n%s\n !=\n%s" % (x, y)
AssertionError: False is not true : 
[[  0   0   0   0   0   0]
 [  0   0   0   0   0   0]
 [  0   0 255 255   0   0]
 [  0   0 255 255   0   0]
 [  0   0   0   0   0   0]
 [  0   0   0   0   0   0]]
 !=
[[255 255 255 255 255 255]
 [255   0   0   0   0 255]
 [255   0 255 255   0 255]
 [255   0 255 255   0 255]
 [255   0   0   0   0 255]
 [255 255 255 255 255 255]]

[rahulporuri]

LGTM. I verified that kiva GraphicsContext expects heigth, width of image to be ints, not floats.

[rahulporuri]

If we can assume that size_or_ary is a tuple of ints, we can make the following change instead (IIUC the code correctly) but we can be defensive and go with the changes you propose.

Suggested change

	scale = kw.pop("dpi", 72.0) / 72.0
	scale = kw.pop("dpi", 72.0) // 72.0

[aaronayres35]

If it's alright with you I think I will leave the current approach, as you mention, to be defensive. The reasoning being that I think scale_ctm can accept floats and size_or_ary is what we specifically want to have integer entries.
I would guess in practice scale will typically be an integer but I am not certain that would always be the case