Add Proc#arity
Merge pull request #1183 from h2so5/proc-arity

Add Proc#arity
rollback stack before executing ensure clause.
catching NameError here is not desirable.
Minor code format changes.
Fix typo.
Merge pull request #1184 from iij/pr-ensure-on-correct-stack

Rollback stack before executing ensure clause.
Merge pull request #1186 from carsonmcdonald/mrbcfixup

Minor format changes and a typo fix
Add mruby-proc-ext
Merge pull request #1187 from h2so5/mruby-proc-ext

Add mruby-proc-ext
Make str_modify public
Merge pull request #1188 from h2so5/make-str_modify-public

Make str_modify public
Add String#swapcase,swapcase!,concat,casecmp,start_with,end_with
Merge pull request #1189 from h2so5/mruby-string-ext-addition

Add mruby-string-ext methods
use ISXDIGIT instead isxdigit on parser.y:3485
Refactor kernel.c and class.c
Merge pull request #1190 from lateau/master

tiny fix on parser.y: change isxdigit to ISXDIGIT
Merge pull request #1191 from h2so5/refactor-kernel-and-class

Refactor kernel.c and class.c
Add a test for respond_to_missing?
Add implementation for respond_to_missing?