update publishing scheme to be able to publish with signed artifacts

maven.publish.gradle

@@ -1,5 +1,4 @@
 apply plugin: 'maven-publish'
-apply plugin: 'signing'
 
 task javadocsJar(type: Jar) {
     classifier = 'javadoc'
@@ -52,8 +51,3 @@ publishing {
         }
     }
 }
-
-signing {
-    useGpgCmd()
-    sign(publishing.publications)
-}

publish.gradle

@@ -14,6 +14,10 @@ bintray {
             name = "${project.version}"
             released = new Date()
             vcsTag = "${project.version}"
+            gpg {
+                sign = true
+                passphrase = project.hasProperty('signing.gnupg.passphrase') ? project.property('signing.gnupg.passphrase') : System.getenv('signing.gnupg.passphrase')
+            }
         }
     }
 }