Initialize Range->edges after cheking `beg` and `end` to prevent segmentation fault.
Enable test for `Range#initialize`.
Remove API mrb_str_catf().
Remove unused function parametes.
Merge pull request #792 from monaka/pr-remove-mrb_str_vcatf

Remove API mrb_str_catf().
Merge pull request #794 from monaka/pr-reduce-unused-function-parameters

Remove unused function parametes.
Merge pull request #788 from masamitsu-murase/modify_range_initialize

Modify range initialize to prevent segmentation fault.