Size of editor about markx

[Carreau]

May I suggest CodeMirror which support Markdown highlighting.
We use it in IPython, and it has an autogrow capability.

[yoavram]

I'll have a look, thanks!

[yoavram]

I changed the editor from PageDown to CodeMirror, see ab20bc5.
Waiting for feeback if this should be merged to the master branch.
You can also add arbitrary pre and post conversion hooks by writing something like in the js console:

addPreCoversionHook(converter, function(text) { return text.replace("GitHub", "[GitHub](http://github.com)") })

which will convert appearances of GitHub in the markdown to markdown links to GitHub site.

/cc @Carreau @karthikram @lsaravia

[lsaravia]

I like the space between lines that has PageDown, but there are other features of CodeMirror that are interesting, line numbers and highlighting. CodeMirror has some problem with math that makes the text italicized between $. And the math is not rendered in the preview pane.

[yoavram]

1. The space between lines can be modified in static/css/codemirror.css by adding a line-height: 200%; or something similar (you can specify percent or em units, I think) in the .CodeMirror-lines class. Let me know what you think is a good default and I'll set it (or you could create a pull-request).
2. The CodeMirror highlighting is not perfect, I'm not sure why it highlights some of the text, but I guess that could be fixed by either digging into it or by using a less intrusive theme (you can see other themes here available here and if there is one you think will be better let me know, I chose the elegant theme because I thought it was neat).
3. The math rendering was a bug - i fixed it in cca50e0.

[yoavram]

Changed line spacing to 150% and merged codemirror branch to master.
Closing this issue.