Remove mrb_class_obj_get
ArduinoDue Target Cosmetic Change

small cosmetic change
Cosmetic improvements of mrbgems documentation

Cosmetic improvements of mrbgems documentation
Implement :core parameter for conf.gem
Apply :core parameter to default.gembox
Apply :core parameter to full-core.gembox
Merge pull request #1224 from h2so5/remove-mrb_class_obj_get

Remove mrb_class_obj_get
Merge pull request #1226 from bovi/patch-1

ArduinoDue Target Cosmetic Change
Merge pull request #1227 from bovi/patch-2

Cosmetic improvements of mrbgems documentation
Merge pull request #1228 from bovi/mrbgems-core-gem

Implementation of :core parameter for conf.gem