Disabling bold / italics with toolbar spawns more * if inner text is selected, not outer

[CosmoMyzrailGorynych]

Version

1.0.2

Test Environment

Firefox Developer Edition (latest), nw.js (webkit latest).

Current Behavior

1. Go to https://nhnent.github.io/tui.editor/ , find an editor with a code input.
2. Write **bold**
3. Double-click the bold. Note that only bold gets selected, not **bold**.
4. Click a Bold button on a toolbar.
5. Now you have ****bold****.

These __bolds__ are selected with underscores on double-clicking, and their formatting is removed correctly. But if exactly bolds are selected, it creates more symbols as well.

The same affects *italics*.

Expected Behavior

You should get bold on step 5. Code editor should check for surrounding asterisks.

[sohee-lee7]

This issue is same #434 and that is fixed. So I close this issue.