.emacs: Some trivial changes.

- Deleted workarounds for UTF-8 based Japanese environments.
- Deleted key-binds which toggles IME by Henkan-key and Muhenkan-key.
- Added key-bind to edit search string in incremental search mode.
  Now we can search Japanese string by this setting.
- Deleted unused setting for Ag.
- Changed face-color for region.
.bashrc: Some trivial changes.

- Changed alias `diff' to use colordiff.
- Added alias `rm' to confirm deleting multiple files.
- Changed alias `clean' to confirm deleting files.