Updates to get_involved

Have made a few minor changes to get_involved which will, I'm afraid, mean that any translations made of those passges will have to be altered otherwise the site won't work properly. I've had to break a couple of paragraphs into two or three entries in en.yml to take account of links or other coding. These changes update Diasporial to new tutorials site, and fix a couple of other errors.

Have added a new class to en.yml called 'click', which styles items for a user to click. This is mainly used in the tutorials, but I have used three of them for hashtags in get_involved, so have included the class in this commit.