[examples] e231 fixes

Signed-off-by: Thomas Hisch <t.hisch@gmail.com>
[examples] fix e241 where it makes sense

Signed-off-by: Thomas Hisch <t.hisch@gmail.com>
MNT : removed *args from CallbackRegistry init

Specified to be removed for 1.5
Merge pull request #3767 from jenshnielsen/doc_fixes

RST fixes for the docs
Merge pull request #3764 from tacaswell/cb_args_deprecate

MNT : removed *args from CallbackRegistry init
Merge pull request #3714 from thisch/pep8fix_e231_e241

[examples] fix pep8 error classes e231 and e241
Merge pull request #3768 from jenshnielsen/mock_backend

DOC : Mock backends when building docs
colorconv from scikit image
Modify colorconv to use local dtype and numpy
Use local colorconv rather than scikit-image
Add scikit image license
Remove Lena examples
use argparse to parse input in make.py
Exclude doc files not in the toc tree
Add option to treat sphinx warnings as errors
treat warnings as errors

When building docs with Travis