Update setup.py to v0.5.1

Author: TomSlater

setup.py

@@ -20,7 +20,7 @@
 setuptools.setup(
     name="particlespy",
     package_dir={'particlespy':'particlespy'},
-    version="0.5.0",
+    version="0.5.1",
     author="Thomas Slater",
     author_email="tjaslater@gmail.com",
     description="A package to perform particle segmentation and analysis",