Fix pyblish/pyblish-lite#59, fix pyblish/pyblish-lite#113

[chadmv]

Reset the iterator to ensure state sync with GUI checkmarks.
Check publish state when processing to skip instances that have been disabled.

[mottosso]

Oh snap, is this it? 4 years of getting emails about this not working xD Thanks for this.

It's unclear why Travis is taking so long, I tried restarting it but it's still hung up. I'll leave this overnight to see whether it just needs a really long time.

[chadmv]

It seemed pretty straightforward. I had to double check everything because the fix seemed relatively simple. But it solved my issue in #113 and fixed the test case presented in #59

[mottosso]

Nice one.

Because this is at risk of affecting the behavior of publishing, I'll release this as a "beta" initially to allow users to test it using:

pip install pyblish-lite
# pyblish_lite-0.8.7 installed

pip install pyblish-lite --pre --upgrade
# pyblish_lite-0.8.8b1 installed