Improvement: open directories (code included)

[janwilamowski]

To see if it would work, I ported and extended the -r flag from the BASH version of rmate. My conclusions: opening many files (more than a dozen or so) is

• slow
• confusing due to the missing folder structure (this could potentially be fixed by having the Sublime plugin replicate the original hierarchy)
• messy with larger directories in which there are many files that shouldn't be opened (binaries, logs etc)

I added rudimentary support for an exclusion list to alleviate the last issue but overall, it doesn't seem very practical to work with. I'm leaving it here anyway in case someone else is interested or wants to give it a shot: sclukey/rmate-python#4