Fix facebook and twitter share buttons

[luisbebop]

Both buttons should get the latest picture of the timeline with a size that fits nicely on the Twitter card and Facebook share.

[bmfreitas]

Hey man, using my Twitter test account, I managed to get this result:

This is the Facebook share:

What do you think?

[luisbebop]

On Twitter the message: "Platform to biomakers ..." replace for the headline of the landing site "Code, create and share ...."

[bmfreitas]

Alright, here is goes:

[luisbebop]

Perfect!