Added SoundCloud tag
First commit.
testing
Added logic to load mathjax only when tag mathjax is present in post and index templates.
Changing names and correcting default values.
Fix Flake 8 issues
Fixed mathjax config description in conf.py.
Added an aditional back slash to ipynb config example.
Make it possible to get help when running the build command.
Merge branch 'master' of https://github.com/ralsina/nikola into command_build_help
Updated changelog.
Merge pull request #319 from okin/command_build_help

Make it possible to get help when running the build command.
solve conflict
get twitter_card and mathjax working on site & default
Added SoundCloud tag
Fix Flake 8 issues
docs and changelog for soundcloud directive
Merge pull request #314 from DoctorMalboro/master

Soundcloud support
Fix Jinja2 URL and some typo
Merge pull request #321 from quijot/patch-1

Fix Jinja2 URL and some typo