Add proxy support for video uri fetching. (youtube-dl seems to get proxy uri from env. variable.
Merge branch 'master' of github.com:shk3/edx-downloader
Merge pull request #10 from iemejia/master

Changes to support subtitle download
Merge branch 'master' of github.com:shk3/edx-downloader
Use 2to3 to make the revision in Merge pull request #9, #10 effective to its python 3 version.
Substitute repetitive download of URLs with a small function.
Use formatted strings to eliminate spurious spaces.

This may (potentially) simplify dual compatibility between python 2 and
python 3, especially when prints are involved.
Upgraded the script to be compatible with python versions superior to 2.6
Added .gitignore file