Improve README.md

[baojjeu]

No description provided.

[edwardloveall]

To be honest, I actually prefer the space after the colon, as is the case in the community ruby style guide:
https://github.com/bbatsov/ruby-style-guide#spaces-operators

Use spaces around operators, after commas, colons and semicolons, around { and before }. Whitespace might be (mostly) irrelevant to the Ruby interpreter, but its proper use is the key to writing easily readable code.

[joaomdmoura]

Great, I'm merging it