v1.1.0

This release includes the following changes:

• Publish with a Google Maps key that only works on farmOS GitHub Pages.
• Layer attribution #73
• Add MapBox watermark and attribution.
• Convert layer visibility to a string before saving it to localStorage with JSON.stringify(). See #65
• Test localStorage layer visibility is a boolean after parsing it with JSON.parse(), in case some browsers convert it to boolean automatically in localStorage.getItem(). See #65
• Explicitly check to see if localStorage.getItem() is not null before syncing it to OpenLayers. See #65