v0.16.0

• 0.16.0 - @matthewrudy
• rubocop -a - @matthewrudy
• Fix undefined memoized_methods error raisied when parent class does not call memoize - @PikachuEXE
• Add support for class-level cache flushing. - @JoeMcB
• Use the latest minitest - @matthewrudy
• use assert_nil to avoid minitest deprecations - @matthewrudy
• Bump 2.2 and 2.3 versions to latest. - @jrafanie
• Add ruby 2.4 to travis - @jrafanie
• Fix travis with jruby-head - @matthewrudy
• Steal the ruby list from the rake travis.yml - @matthewrudy
• ruby < 1.9.3 needs an older version of rake - @matthewrudy
• Add return in comments for flush_cache. - @joshuapinter
• Use https instead http - @biow0lf