Update language level from 1.7 to 1.8
Replace explicit types with <> (main)
Replace explicit types with <> (test)
Use lambda expressions where possible (main)
Use lambda expressions where possible (test)
Replace external iteration with stream API (main)
Replace external iteration with stream API (test)
Merge pull request #348 from spring-io/jdk8-lang

Use JDK 8 language features