moving from Guava's Optional to java8 java.util.Optional
JsonNode[] no method fixed
NPE when no parent context available
fixing Jacoco dependency with Java
Oracle 8 used in Travis configuration
couple of lambdas
commenting out shade plugin since it is not currently available from Java 8
using lambda for a thread shutdown hook
Merge branch 'java8' into develop

Conflicts:
	baobab-core/src/main/java/net/milanaleksic/baobab/builders/IncludeBuilder.java