Style elements are implicit in their tags

Prepare for a lengthy description.

Some tags such as B and STRONG etc. have their style implicit in their NodeType so if they have additional styling, this plugin should not convert them to a strong.


For example, if you paste:
```<strong style="font-weight: bold; margin-bottom: 0px; color: rgb(51, 51, 51); font-family: 'Guardian Egyptian Text', Georgia, serif; font-size: 16px; font-style: normal; font-variant: normal; letter-spacing: normal; line-height: 24px; orphans: auto; text-align: left; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(246, 246, 246);">emphasis</strong>```

The plugin will read the ```font-weight``` and turn the text node into a B element. This is clearly not correct, as you'll then end up with ```<strong><b>text</b></strong>```.

This pull requests solves the problem by creating a list of elements that should not be wrapped e.g STRONG, B, etc. and skipping over them. Another way to do it is to convert the element into a B and then check it but I'm not really sure which one is the best. Also my list of elements might be a little incomplete.

\cc @theefer @robinedman @rrees