Support Guice 4

[mrpotes]

When trying to use Guartz with Guice 4, you get the following exception:

java.lang.ClassNotFoundException: com.google.inject.internal.util.$Preconditions
	at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	at org.eclipse.jetty.webapp.WebAppClassLoader.loadClass(WebAppClassLoader.java:560)
	at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
	at org.nnsoft.guice.guartz.QuartzModule.configure(QuartzModule.java:59)
	at com.google.inject.AbstractModule.configure(AbstractModule.java:62)
...

This is because Guice 4 uses Guava, rather than having internal classes that it has to maintain. Please can you accept these contributions from @awillinger to uplift versions.