[Release 0.5.8] Update version to 0.5.8 (#191)

gradle.properties

diff --git a/gradle.properties b/gradle.properties
index 80a35f8..fcc9b82 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -17,4 +17,4 @@
 # under the License.
 #
 
-version=0.5.8-SNAPSHOT
+version=0.5.8