Merge pull request #112 from wanabe/fix-test-script-path

Fix ENV to fit current name of scripts directory: "lib/mrb/scripts"

Patch by wanabe. Thanks!!!
Merge pull request #113 from wanabe/mruby-scaninfo-put_index

Wrap grn_scan_info_put_index() in ruby method

Patch by wanabe. Thanks!!!
Merge pull request #115 from wanabe/mruby-define-grn_obj-class

mruby: Define Groonga::Object for wrapper of grn_obj

Patch by wanabe. Thanks!!!
Wrap grn_expr_code_get_weight() in ruby method
Make ruby instance of grn_expr_code in scan_info_build()