Add style changes per @Fryguy

1. Remove jruby & rubinius 1.8 statements from .travis.yml
and add rubinius 2.
2. Undo attempts to fix Rubocop "void context" warnings which
result in redundant code in tests.
3. Simplify validate_definition_entry_modifier & rename to
valid_definition_entry_modifier? since it doesn't raise an exception
4. Simplify get_size
5. Align assignments in constant definitions when possible.
6. Remove unnecessary "()" in new lambda syntax.