Rio-tiler

* Update sentinel2-cogs image path (https://github.com/cogeotiff/rio-tiler-pds/pull/22).
* Remove ContextManager requirement in base class and update for rio-tiler 2.0b13 (https://github.com/cogeotiff/rio-tiler/pull/265).
* Add MODIS (PDS and Astraea) dataset (https://github.com/cogeotiff/rio-tiler-pds/issues/18)
* move reader base classes to rio-tiler (https://github.com/cogeotiff/rio-tiler-pds/issues/24)
* add missing `0` (e.g "B1" -> "B01") when user forget it on sentinel and modis band names (https://github.com/cogeotiff/rio-tiler-pds/issues/25)

* add support for CBERS-4A (author fredliporace)

* update python versions support

* avoid `nodata` options colision with kwargs in L8Reader

* Fix polygon and point coordinates in `pixels_encoder`

**breaking changes**

* remove python 3.6 support

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- Fix Sentinel-2 bad AWS url