Merge pull request #301 from tonysyu/viewer-user-guide

DOC: Add Viewer Quickstart to User Guide.
Fix bug in binary dilation and test case
Add test case for non-square images
Merge pull request #310 from ahojnnes/morph

BUG: Fix bug in grey erosion and dilation.
TST: Invoke Travis nosetests differently.
DOC: suppress plot display in doctests

Plot display interrupts the doctest run.
DOC: Fix block-formatting in doctest
DOC: Fix doctests in io collection module
DOC: Fix array formatting in doctest
DOC: Fix doctests in viewer subpackage

The doctests in the viewer subpackage weren't originally written as proper doctests.
DOC: Add missing import in doctest
DOC: Fix doctests in lpi_filter
DOC: rewrap docstring lines and remove unused import
DOC: fix numpy dtype print out.

This fix may be very dependent on numpy version since print out has change over time.
Merge pull request #314 from tonysyu/doctest-fixes

Doctest fixes
DOC: Replace doctest with literal code block
DOC: Remove plots from docstring examples

Plotting isn't really necessary in a docstring example. Both of these functions already have gallery examples.
Merge pull request #315 from tonysyu/doctest-plot-fix

DOC: Remove plotting from docstring examples.
ENH: Bool dtype conversion speed improvements.
Conversion to bool: threshold on half dtype max.