Fix close button positioning

Adjust spacing and move it to the right side, like in Linkinius
inlineImageCell has overflow: hidden

This prevents a useless scrollbar from appearing
Add highlight around inline nicknames
Merge pull request #12 from paradox460/distinguish-inline-usernames

Add highlight around inline nicknames
Merge pull request #14 from paradox460/fix-image-scroll-bug

Prevent phantom scrollbar from appearing on inline images
Merge pull request #13 from paradox460/fix-close-button

Fix close button spacing and positioning