Ws tag prevents startup outside servlet-container environment

[alexvigdor]

The Ws websocket client tag depends on the java websocket API and will break startup if that API is not present, which may be the case outside of a servlet container.

com.disney.groovity.Taggable: Provider com.disney.groovity.tags.Ws could not be instantiated: java.util.ServiceConfigurationError
java.util.ServiceConfigurationError: com.disney.groovity.Taggable: Provider com.disney.groovity.tags.Ws could not be instantiated
	at java.util.ServiceLoader.fail(ServiceLoader.java:232)
	at java.util.ServiceLoader.access$100(ServiceLoader.java:185)
	at java.util.ServiceLoader$LazyIterator.nextService(ServiceLoader.java:384)
	at java.util.ServiceLoader$LazyIterator.next(ServiceLoader.java:404)
	at java.util.ServiceLoader$1.next(ServiceLoader.java:480)
	at com.disney.groovity.Taggables.init(Taggables.java:75)
	at com.disney.groovity.Groovity.init(Groovity.java:381)
	at com.disney.groovity.Groovity.start(Groovity.java:441)
	at com.disney.groovity.GroovityBuilder.build(GroovityBuilder.java:342)
	at com.disney.groovity.GroovityBuilder.build(GroovityBuilder.java:251)
	at com.disney.groovity.aws.lambda.GroovityAwsLambda.<init>(GroovityAwsLambda.java:70)
	at com.disney.groovity.aws.lambda.GroovityAwsLambda.<init>(GroovityAwsLambda.java:32)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
Caused by: java.lang.NoClassDefFoundError: javax/websocket/ClientEndpointConfig$Configurator
	at java.lang.Class.getDeclaredConstructors0(Native Method)
	at java.lang.Class.privateGetDeclaredConstructors(Class.java:2671)
	at java.lang.Class.getConstructor0(Class.java:3075)
	at java.lang.Class.newInstance(Class.java:412)
	at java.util.ServiceLoader$LazyIterator.nextService(ServiceLoader.java:380)
	... 13 more
Caused by: java.lang.ClassNotFoundException: javax.websocket.ClientEndpointConfig$Configurator
	at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	... 18 more

While this can be worked around by explicitly importing javax.websocket-client-api as a dependency, it might make sense to move the Ws tag out of groovity-core, either into groovity-servlet or a standalone module.