Merge branch 'mrbgem_summary' of https://github.com/take-cheeze/mruby into take-cheeze-mrbgem_summary

Merge branch 'refactor-enumerable.rb' of https://github.com/suzukaze/mruby into suzukaze-refactor-enumerable.rb

add unit tests for NilClass

make Enumerable methods to support multiple values; collect, detect, each_with_index, find_all, inject, max, min, partition, reject, sort

Add test enumerable.rb

fix bool number to macro

fix bug when `0 + other object`

fix bug when `0 * other object`

Refactor assert_true

float + nil should be raise TypeError

Unify indent style

Add Fiber's double resume test and fix it.