New earth image plus minor fixes to main pages

[goobertron]

A few minor changes to the main three pages.

• earth image on front page is less deep
• fixed a few links and minor grammatical fixes

[goobertron]

Two further commits to undo changes to files which have already been committed in the tutorials branch:

https://github.com/goobertron/diaspora-project-site/commit/deb8cb7d4d2759d4e0b170ccc51ebd97e0ca5813

https://github.com/goobertron/diaspora-project-site/commit/5c199f55d3ffbefb84ba4523e6cbca886d8bf237

Sorry, I've made a bit of a mess of this. I've really tried to do it correctly! I hope it works out OK.

[jhass]

You shouldn't have committed to master, it should always stay the same as upstream to give you a sane local base. Lets fix it:

git remote add upstream git://github.com/diaspora/diaspora-project-site.git
git fetch upstream
git checkout master
git branch -m master minor_updates
git cherry-pick deb8cb7d4d2759d4e0b170ccc51ebd97e0ca5813
git cherry-pick 5c199f55d3ffbefb84ba4523e6cbca886d8bf237
git checkout -b master upstream/master
git push -f origin master minor_updates

Then please open a new pull request from the new minor_updates branch.