Bump up to v0.5.0-SNAPSHOT

Author: dmikurube

build.gradle

@@ -21,7 +21,7 @@ sourceCompatibility = 1.8
 targetCompatibility = 1.8
 
 group = "org.embulk"
-version = "0.4.1-SNAPSHOT"
+version = "0.5.0-SNAPSHOT"
 description = "Reads files stored on Google Cloud Storage."
 
 tasks.withType(JavaCompile) {