Adding current releases to "News" section

[DietBru]

Hi, I noticed that the News section on the home page was not updated for quite some while. So I

• added the releases 1.6 - 1.7.1,
• removed releases < 1.4 (to make the News section not too long) and
• fixed two minor HTML problems (flagged by PyCharm).

[oscarbenjamin]

Thanks. I guess this should be part of the release script but I'll do this manually for future releases in the mean time.