Modernize code

[rhuffman]

Update to Java 8 idioms and remove warnings that show up in Intellij.

This includes:

• replacing the Guava Predicate and Function usages with standard Java Predicate and Function classes
• removing unnecessary generic type declarations
• restricting access to some methods
• adding @Suppress annotation for methods and classes that are not used in the code but must be public for the library to be used
• replacing anonymous inner classes (Callables, Runnables, and Predicates) with Java 8 lambdas

Fixes #15