[REL] Release 0.5.2 (#216)
[REL] Release 0.5.2 (#216)

Bump notices in changelog from next -> 0.5.2

Summary of changes since 0.5.1

* Test and example files in serpentTools.data module and can be 
  loaded with serpentTools.readDataFile
* Hexagonal mesh plot for hexagonal detectors
* Detector and Depletion readers can access detectors and materials,
  respectively, with reader[objName]
* Better x and y labels for detector plots
CORE-GATECH-GROUP/serpent-tools,CORE-GATECH-GROUP/serpent-tools