Update requirements.

requirements.txt

-matplotlib==2.1.2
-numpy==1.11.0
-rasterio==0.36.0
-Fiona==1.7.11.post2
-Shapely==1.6.4.post1
-rasterstats==0.12.1
-sentinelhub==2.0.3
-sentinelsat==0.12.2
-pyproj==1.9.5.1
-typing==3.6.6
+matplotlib>=2.1.2
+numpy>=1.11.0
+rasterio>=0.36.0
+Fiona>=1.7.11.post2
+Shapely>=1.6.4.post1
+rasterstats>=0.12.1
+sentinelhub>=2.0.3
+sentinelsat>=0.12.2
+pyproj>=1.9.5.1
+typing>=3.6.6