Merge pull request #28 from jtulach/master

Eliminating need for agent
Test forking during release
Call Retrolamdba directly from the Maven plugin, without reflection

 We have to run Retrolambda on itself, because the Maven plugin requires Java 6
 and would not otherwise compile against Retrolambda's Java 8 classes.
Refactored
Fixed the Maven plugin not working under Java 6

- Main no longer requires Java 8 classes during its class loading
- Forces the process to fork when not under Java 8
The use of a Java agent is now optional

Closes #27
Refactored: install the dumper only once, removed duplication
Typo
Refactored: extracted irrelevant stuff from the virtual file system
Updated project files

Run also Maven with Java 6 to test the plugin and the agent mechanism
Refactored: extracted LambdaClassSaver
Fixed main classes not included in the test classpath
Added @since 1.6.0
Release 1.6.0
Prepare for next development iteration
Improved docs
Use a non-delegating class loader to support transforming classes with same name as JRE's built-in classes

Fixes #29
Merge branch
Merge tests
retrolambda/pom.xml