prepping for 5.1.2 release (#187)

* prepping 5.1.2 release

* updated changelog

CHANGELOG.md

@@ -35,6 +35,10 @@ release.
 
 ## [Unreleased]
 
+## [1.5.2]() 
+
+- Made gdal an optional dependency. [#186](https://github.com/USGS-Astrogeology/plio/pull/186)
+
 ## [1.5.1]()
 
 ### Fixed

setup.py

@@ -8,7 +8,7 @@ with open('README.md', 'r') as f:
 def setup_package():
     setup(
         name = "plio",
-        version = '1.5.1',
+        version = '1.5.2',
         author = "USGS Astrogeology",
         author_email = "jlaura@usgs.gov",
         description = ("I/O API to support planetary data formats."),