Switching to a dynamic, information-rich homepage

[tompollard]

We should consider switching to a dynamic, information-rich homepage to replace the big grey image.

The goal would be to actively present useful/interesting information to our users, rather than making them dig around.

We could highlight:

• New data, software, models, etc
• Latest news and announcements
• Calls for action (e.g. help us to annotate x, etc).
• Publications that make use of PhysioNet content
• Perhaps leaderboards on benchmark datasets (once benchmarks are added)
• ...