Add Hash#flatten
Merge pull request #2186 from suzukaze/add-hash.flatten

Add Hash#flatten
Add document of header searcher of compiler.
Merge pull request #2187 from take-cheeze/header_searcher_doc

Add document of header searcher of compiler.
Don't reset ridx,eidx. And fix for #1949
Merge pull request #2188 from takeru/dont_reset_ridx_eidx

Don't reset ridx,eidx. And fix for #1949
Refactoring exception test.

Change to use assert_equal explicitly.
Merge pull request #2191 from yui-knk/refactor-exc-test

Refactoring exception test.
Add Hash#invert
Refactor mrb_str_capitalize_bang()
Refactor mrb_str_downcase_bang()
Refactor mrb_str_split_m()
Refactor mrb_str_upcase_bang
Refacotr mrb_str_substr()
Refactor mrb_str_hash()
Fix indents in mrb_str_inspect() of string.c
Refactor read_lineno_record_1() in load.c
Merge pull request #2192 from suzukaze/add-hash.invert

Add Hash#invert
Merge pull request #2193 from suzukaze/refactor-string.c

Use mrb_bool instead of mrb_int  in string.c
Merge pull request #2195 from suzukaze/fix-indent-string.c

Fix indents in mrb_str_inspect() of string.c