Merge pull request #224 from yferrer/master

Adding example on how to change tiles depending on zoom level.
feat(test): Completed e2e tests for the bounds example.
Small changes on protractor tests
feat(test): Added an e2e test to the custom-parameters-example.html
feat(test): Added a test for the googlemaps-example.html

To avoid problems like the reported by @pwoloszum here:
https://github.com/tombatossals/angular-leaflet-directive/issues/223
Merge pull request #225 from yagoferrer/master

fix(build): Fixed bug where you couldn't make visible a group of markers (overlay) created as not visible by default. Added example on how to create groups of markers and how to make them visible / not visible on demand.
fix(grunt): Added the e2e protractor tests to the Grunt watch cycle.
New version
feat(examples): Make the buttons toggable on the marker-groups-example.html made by @yagoferrer here:

https://github.com/tombatossals/angular-leaflet-directive/pull/225
fix(test): Updated e2e tests to pass the jshint validations