Add some tests for render/view

[erbridge]

The single cursor tests are failing, probably due to a bug in text.Region.Intersection.
ViewRegionMap still needs testing.

[quarnster]

view_test.go:105: Test 1: Expected [(100, 100)], but got [(0, 0)]
view_test.go:105: Test 2: Expected [(100, 100)], but got []
view_test.go:105: Test 3: Expected [(100, 100)], but got []
view_test.go:105: Test 4: Expected [(150, 150)], but got []
view_test.go:105: Test 5: Expected [(100, 100)], but got []

They should all be [] because there's nothing to render for empty regions. (Cursors are handled elsewhere).

text.Region.Intersection is actually behaving correctly, try running this in the ST3 console: a = sublime.Region(100,100); b = sublime.Region(100,100); a.intersection(b) and the output is (0, 0).

render.ViewRegions.Cull should check the returned intersection region if it's empty before adding it to fix test 1.

[erbridge]

That seems a bit weird to me. The intersection of the two regions is the cursor. I can understand that we'd want to exclude them, though, so although I still think text.Region.Intersection is misbehaving, I'll fix these tests.

[quarnster]

IMO you are correct regarding Intersection, especially as intersects returns true for the same input, but let's not fix it until it proves to be a problem simply because it's what ST3 does.

[coveralls]

Coverage increased (+0.91%) when pulling f6e0bcd on erbridge:render_view_test into f349b59 on limetext:master.