RmdIsInRCode fix

I was not able to send line to R (\l) from Rmd. Looks like the problem is in RmdIsInRCode. Please consider the following fix. Thanks.
Merge pull request #13 from genrich/patch-1

Fix chunk recognition.
Fix terminal application name on Mac OS X.
Merge pull request #15 from chiphogg/master

Option to disable insert-mode commands
Update information about colorout package.
Add ftplugin/rmd.vim and ftplugin/rrst.vim.
Recognize '@' as keyword character.
Ensure that source() is from base package.
More information about vimcom package.
New option: vimrplugin_only_in_tmux.
Don't require knitr: vimcom already requires it.
Set filetype instead of just reading syntax/r.vim.
Do omnicompletion even if vimcom isn't installed.
Update knitr chunk options.
Improve support to Markdown file type.
 + Improve syntax highlight.
 + Improve indentation of list items.
 + Build and open html file.
 + Build odt file.
 + GVim menu items for html and odt.
Add "." to iskeyword.
New option: vimrplugin_rmhidden.
Avoid "No menu RSendFile" error.
New indent scripts for rmd and rrst.
Add syntax and indent scripts for rmd and rrst.