Format README as Markdown

[mfhepp]

Hi, it would be good to format the README as Markdown so that the Github repository page looks a bit nicer.

[metov]

I took a stab at this in #528

[metov]

Oh shoot, should have checked before raising it - looks like we already have:

• Format Readme using Markdown #519
• make README a markdown document #467
• Change README format to Markdown #327

[miketheman]

Appears to be resolved via 99d27e7 - recommend closing this issue.