Add MovingPandas minimum version info

Author: anitagraser

README.md

@@ -11,7 +11,7 @@ The Trajectools plugin adds mobility data analysis algorithms to the QGIS Proces
 
 ## Requirements
 
-Trajectools requires [MovingPandas](https://github.com/movingpandas/movingpandas) (a Python library for movement data analysis) and optionally integrates [scikit-mobility](https://scikit-mobility.github.io/scikit-mobility/) (for privacy tests), [stonesoup](https://stonesoup.readthedocs.io/) (for smoothing), and [gtfs_functions](https://github.com/Bondify/gtfs_functions) (for GTFS data support). 
+Trajectools requires [MovingPandas](https://github.com/movingpandas/movingpandas) >= 0.21.2 and optionally integrates [scikit-mobility](https://scikit-mobility.github.io/scikit-mobility/) (for privacy tests), [stonesoup](https://stonesoup.readthedocs.io/) (for smoothing), and [gtfs_functions](https://github.com/Bondify/gtfs_functions) (for GTFS data support). 
 
 ### Conda install