Fix markdown preview height. Some styles crept back in during merge.
Fix markdown preview height. Some styles crept back in during merge.

sctlee/markdown-preview,danielgtaylor/atom-api-blueprint-preview,ArnaudRinquin/markdown-preview,grimmer0125/markdown-preview-kramdown,Galadirith/markdown-preview,makyo/markdown-preview,atom/markdown-preview,rugk/markdown-preview,tkssharma/markdown-preview