remove unnecessary depedency in test build
need not to initialize ci->err at toplevel
Test for raise in ensure
Merge pull request #1643 from take-cheeze/remove_unnecessary_depedency

Reduce unnecessary mrbgems full test rebuild.
Merge pull request #1644 from carsonmcdonald/testraiseinensure

Test for raise in ensure
tests for "case" expression.
adjust proc->target_class according to surrounding proc->target_class; based on a patch from @Fleurer; close #1627
small cosmetic variable renaming
small refactoring (dedup mrb_vm_cv_set)
Merge pull request #1645 from iij/pr-case-expression-test

tests for "case" expression.
Merge branch 'master' of github.com:mruby/mruby
Add mruby-string-utf8
Merge branch 'mruby-string-utf8' of https://github.com/mattn/mruby into mattn-mruby-string-utf8
mruby-string-utf8: UTF-8 string may contail NUL; #1646
mruby-string-utf8: redefine String#size for UTF-8 string; #1646
Remove duplicate test
Merge pull request #1647 from mattn/remove_duplicate_test_for_mruby_string_utf8

Remove duplicate test for mruby-string-utf8