Use unicode-display_width on calculating display width

[Bugfire]

Annotate model create wrong indentation when column comment has some characters.

• Almost kanji characters are represented by 3bytes.
• Some normal-width symbols are represented by 3bytes.
• Emojis and some kanji characters are represented by 4bytes.

'unicode-display_width' gem is working for calculating width properly for me.

Following is a indented spec diff with some characters.

Following is the result of rake spec on current develop branch and above spec diff.

Calculating width by the gem and above spec diff work properly.