vote to ignore plugins and platforms dir

[morenoh149]

makes no sense to put these dirs into version control

[diegonetto]

There is an open question (#29) that would benefit from this. I had suggested ignoring the platforms directory and I think leaving out plugins is a good idea too, but you've modified the wrong file.

A little justification would have been nice but I linked to a Stack Overflow post in #29 that describes how to install plugins from a Cordova hook and follow best practices.