GrahamA: tested with most recent jdk ea build.
Describe each of the remaining kinds of method references available.
GrahamA: add license headers, remove main method used as a scratchpad.
Ignore more intellij files.
Introduce asm to help verify that method references have been used.
First example complete. A matcher that checks you're using method references by discovering the java source file from the class, scans the filesystem, and reads the source to check there's a :: before the method name. Phew.
Make the name of test consistent with the category of method reference as described in introduction.
Add an example for a reference to a static method.

Conflicts:
	src/main/java/org/adoptopenjdk/lambda/tutorial/exercise4/Printers.java
Formatting.
Add test case for using method references to invoke methods on a particular instance.
Add test case to show how to use method reference using 'this'.
Whoops, forgot to remove blankPage variable from when figuring out what this test should do.
Add correctly failing test for using constructor method reference.
Finish javadoc for final test of method references chapter.
Minor fixes to Javadoc and add a license statement