v0.6.13

• updates documentation (c8a9799)
• creates hiding-colorscale example (a69a896)
• improves custom-tiles example (98a25ca)
• fixes cartodb tile detection (1c5db3e)
• adds basic tile map attributions (closes #35) (5d6907c)
• updates d3-tile to v1.0.0 (88c2756)
• updates minor d3 dependencies (820f190)
• updates to topojson-client v3.1.0 (f98729a)
• updates minor d3plus dependencies (e1d1426)