Add Support to build loadable modules defined in mrbgems.
Apply @masuidrive's review point. @bins should be Array.
fix handling of :branch option of gem.conf
add mrbgems/mruby-string-ext, and method: String#getbyte
Merge pull request #961 from monaka/pr-support-user-defined-loadable-build

Add Support to build loadable modules defined in mrbgems.
Merge pull request #963 from skandhas/pr-add-mrbgems-mruby-string-ext

add mrbgems/mruby-string-ext, and method: String#getbyte
Merge pull request #962 from masahino/fix_branch_option

fix handling of :branch option of gem.conf
mrbc: exit if outfile is specified multiple times
unify mrb_ary_new{,_elts,_from_values}; mrb_ary_from_values() is a winner
Add String#dump method.
Merge pull request #965 from cremno/mrbc-multiple-outfiles-mem-leak

mrbc: exit if "-o" is specified multiple times
Merge pull request #966 from monaka/pr-add-dump-method-to-String-class

Add String#dump method.
add "strip" family to String.
add mrbgems/ext/mruby-numeric, and method: Integer#chr
add Integer#chr test case: multibyte (raise RangeError)
fix comment
Fixed #969
Merge pull request #967 from iij/pr-string-strip

add "strip" family methods of String to mruby-string-ext
Merge pull request #968 from kouki-o-iij/pr-mrbgem-numeric-ext

add mrbgems/ext/mruby-numeric, and method: Integer#chr
Merge pull request #970 from masuidrive/fix_building_script

Fixed #969