Update the outdated "Rebase Strategy" section.

We now points to the wiki page which contains the latest changes.
Minor Getting Started docs fixes

Noticed when reviewing the site again on staging.
Merge pull request #61 from townxelliot/minor-docs-fixes

Minor Getting Started docs fixes
Clean up download tables

Some of the rows had too many columns, now that I've moved
the installation instructions into Getting Started and just
have a generic link at the top of each download page.
Minor grammatical fixes for 'Canaries' download page
Move link to instructions to a consistent position
Merge pull request #62 from townxelliot/download-pages-broken

Fixes for download pages
Merge pull request #53 from darktears/update-rebase-strategy

Update the outdated "Rebase Strategy" section.