fixed gradle file

tlatools/build.gradle

@@ -12,6 +12,7 @@ repositories {
 }
 
 dependencies {
+	compile files ('lib/javax.mail.jar')
 	testCompile files ('lib/easymock-3.3.1.jar', 'lib/jpf.jar', 'lib/junit-4.8.2.jar', 'lib/javax.mail.jar')
 }