Add print plugin, use npm package via yarn

[thet]

• Add the print plugin per default, so that images are loaded before the page is going to be printed.
• Use the npm package and yarn to install lazysizes for a defined way to update / add resources. Via .yarnrc a custom location instead node_modules is defined.

Fixes #50

[thet]

The string in int cast is necessary. The tests passed before this change for metadata version 9 only by the way strings are compared in python. See below:

Comparison of "10" with other numbers-as-strings:

>>> "10" >= "0"
True
>>> "10" >= "1"
True
>>> "10" >= "2"
False
>>> "10" >= "3"
False
>>> "10" >= "4"
False
>>> "10" >= "5"
False
>>> "10" >= "6"
False
>>> "10" >= "7"
False
>>> "10" >= "8"
False
>>> "10" >= "9"
False
>>> "10" >= "10"
True

Comparison of "9" with other numbers-as-strings:

>>> "9" >= "0"
True
>>> "9" >= "1"
True
>>> "9" >= "2"
True
>>> "9" >= "3"
True
>>> "9" >= "4"
True
>>> "9" >= "5"
True
>>> "9" >= "6"
True
>>> "9" >= "7"
True
>>> "9" >= "8"
True
>>> "9" >= "9"
True
>>> "9" >= "10"
True

[thet]

travis tests are failing in the moment because of the Plone 4.3 integration.

I don't like having the jsregistry.xml GS profile file around for Plone 5.x - this is registering the resources into the plone-legacy bundle - along with the registration of the lazysizes bundle. That way we end up with a double reigstration of these resources.
I'd actually vote to remove the Plone 4.3 support. Or doing the registration with separate 4.3 and 5.x profiles, as I did for my initial Plone 5.x support PR.

Any comments?

[rodfersou]

please, use sc.recipe.staticresources https://github.com/simplesconsultoria/sc.recipe.staticresources and webpack for this (we are migrating all of our addons to use it)

[hvelarde]

after merging #53 this is no longer the way to fix this issue.

[hvelarde]

superseded by #59