0.7.0 Switch to rasterio

This release significantly changes in the dependencies of localtileserver (switching from GDAL to rasterio), focuses on geospatial applications by dropping non-geo support, includes optimizations to TileClient to avoid REST operations, and majorly refactors the internal code for future development.

What's Changed

• Switch to rasterio by @banesullivan in #154
• Internal refactoring by @banesullivan in #155
• An improved TileClient that avoids the REST interface where possible by @banesullivan in #156

Full Changelog: 0.6.4...0.7.0