Add test of $0 value in bin/mruby related to #2103 .
Merge pull request #2106 from mirichi/enhance

OP_SEND refactoring
Add Array#insert
Array#insert: simpler (and faster) implementation; ref #2107
Merge pull request #2105 from take-cheeze/issue_2103_test

Add test of $0 value in bin/mruby related to #2103 .
Merge remote-tracking branch 'remotes/mruby/master' into enhance
fixed.