Fix Range#size results

Fix condition of Range#include?

Doc

bundled testing gems do not need to be included in default.gembox.
all gems under mrbgems are linked automatically in the test process.

Inline structures have no instance variables, no finalizer, and offer as much space as possible in RBASIC object. This means 24 bytes on 64-bit platforms and 12 bytes on 32-bit platforms.
mruby-inline-struct gem is only provided for testing.

Remove webhook notification for Travis CI

Ranges should not rewrite

As travis-rubies now uses 3 Mac jobs to create archives for various OS
releases.

This is a bit wasteful if multiple builds pass in a short period.

Instead, Travis CI is now running a nightly build of mruby-head
(around 22:30 UTC). This will happen regardless of the state of the
master branch.

Correct argument specifications for few methods

 - Struct#values_at
 - Module#define_method
 - String#chop
 - String#chop!

Fixed by Alex Snaps and reported by Mathieu Leduc-Hamel,
both from shopify.com.  Thank you!

Reported from from Alex Snaps via Mathieu Leduc-Hamel,
both from shopify.com.  Thank you!

Reported from Alex Snaps via Mathieu Leduc-Hamel,
both from shopify.com.  Thank you!

Class#to_s used to return same string repeatedly,
that mean you can modify "class name" by modifying
the return value from Class#to_s.

Solves #2132.

Module#define_method supports proc argument

Reimplement Enumerable#cycle 

Fix pattern of infinite loop
And support all specs in https://github.com/ruby/spec/blob/27960d06e0ce92c37f074450f0eab4b0519b118c/core/enumerable/cycle_spec.rb without Enumerable#size

test/assert.rb should not use puts

Add mrb_class_defined_under