Merge branch 'master' of https://github.com/mruby/mruby
Merge branch 'master' of https://github.com/mruby/mruby
remove mrb_str_each_line form src/string.c
Merge pull request #725 from skandhas/pr-remove-each_line

remove mrb_str_each_line
should be flatten.
build gems if build_config.rb is modified.
note about $MRUBY_CONFIG.
Merge pull request #726 from mattn/fix_build_tasks

Fix build tasks
Merge pull request #727 from mattn/dep_gems

Add dependency to build gems list