Make minor appearance changes to the members page.

Looks like I have different versions of the required dependencies,
which did not match those specified in our current Gemfile.lock.
Hence `jekyll build` would break for me.

Adding Gemfile.lock to .gitignore to allow people to use different
versions of gem dependencies. (After all, we are only just
generating static html pages with bundler probably isn't that
important that we all use the same versions of stuff...)

Also created a basic nav

See test.md for info