Add weighted voting module

[satyamakgec]

No description provided.

[coveralls]

Coverage remained the same at 95.134% when pulling 04fbdcc on weighted-voting-module into 47624d8 on dev-3.0.0.

[satyamakgec]

Everything is fixed only one thing remains i.e proposalId starts from 0. I keep that as it is because if I start with it 0 then there is no way to restrict the user to vote again until unless I will use another storage variable to keep track of it. IMO it is best over introducing another variable to do it.