Pagination Component

[langdonx]

Take a look and let me know what you think. Some things of note:

• It's not as customizable as UI Bootstrap's implementation, but I don't know that the extra options they provide are a good thing, as they have the potential to limit usability.
• There's no 2-way binding at all (yay), but I did have to pull in $scope to $watch the bindings for changes and regenerate which pages are displayed. I don't know of a way around this.
• The way I chose to implement visible-page-buffer might be controversial, but I strongly think that it provides the best usability possible. It always bothered me that UI Bootstrap's implementation jumped around under my mouse as I clicked through pages. I think clicking a moving target is a UX anti-pattern.
• The logic in buildPages() is fuzzy. The algorithm could certainly be improved--it was adapted from PHP I wrote some 10+ years ago, but it's solid and handles all scenarios I've thrown at it in the past as well as some tests I had running earlier using ng-repeat="items in $ctrl.generateRange(100)" and variations of other attributes.
• There are some comments in src/library/pagination/pagination.scss. I left the CSS there because I think it helps usability, but I didn't like hard-coding those color values.
• I had to adjust the columns on the demo page to account for the larger footprint of ngbs-pagination. See src/docs/utils/demo/demo.html.
• VS Code insisted on formatting my HTML with 4 spaces. I can fix if that's an issue.

[langdonx]

This resolves #28.

[langdonx]

Resolved the issues we discussed above:

• Removed unnecessary constructor assignments.
• Switched to $onChanges. I was surprised to see that it fires before $onInit, so I had to move defaults to $onChanges, but left validation errors in $onInit so the console isn't flooded with them.
• Improved documentation to hopefully make things more clear. I tried to convey items is the number of things from their own dataset.
• Improved the demo by reducing the number of pagination components displayed and adding inputs to control rendering.

Let me know if I missed anything, you catch any other weirdness, or you have any other ideas. We could probably add more options, but it seems like a good start.

[IdanCo]

Thank you so much for the awesome work!

[IdanCo]

btw - $onChanges receives a changeObject with a flag indicating the controller is initializing. But it can easily wait for the next PR...