Doesn't work well with breakout plugin

[NdYAG]

Reproduce bug:

1. input ## title, block type changes to h2, (markless works well)
2. press Enter
3. keep typing, the next block type is still h2, instead of unstyled (breakout fails)

Reason https://github.com/icelab/draft-js-block-breakout-plugin/blob/master/src/index.js#L59

breakout-plugin use const atEndOfBlock = (endOffset === currentBlock.getCharacterList().count()) to check if is atEndOfBlock, while markless didn't modify charaterList in changeCurrentBlockType:

https://github.com/r7kamura/draft-js-markless-plugin/blob/master/src/create-markless-plugin.js#L18

in the above h2 case, getCharacterList().count() is 7, but it should be 5 on hitting return.

I think it would be better to remove ## token and it's related charaterlist.

Modifier.removeRange would be a good choice.

[r7kamura]

@NdYAG Thank you for the information! I'll try to fix it 🐛 🔍