-i to use public key instead of private key

[shadiakiki1986]

Hello. I wrote up some code to fix #19.

It deprecates using private keys in favor of using public keys.

The problem is that I could neither install the project dependencies, nor build it, nor run the tests. I'm not sure if it's just something that I'm screwing up as I'm a golang newbie or something else.

I also tried adding some instructions in the readme about how to "build from source".

It would probably be a good idea to install dependencies via godep (example reference)

Edit 1: related to build fail: Issue #32 and #16

Edit 2: related issue to #19 is #9

[AgrawalAmey]

@webvictim this would be a great feature to have, can we merge this if possible?