DAO solidity contract, how to destribute voting rights?

Question

I`m developing a DAO contract on the ropsten testnet with solidity. As with all DAO contracts, people can contribute to the contract and receive the relative amount of tokens based on their contribution.

After the administrator of the contract creates proposals, the token holders can vote on a particular proposal and they should do so with the weighted vote which is proportional to the number of tokens they hold / total supply of tokens.

This is where I run into some trouble trying to figure out the right way to assign a weighted vote system, so that contributors with more tokens have greater weight to their vote.

For example, if the total supply is 100 000 000 tokens and the first contributor has 1000 tokens that would make him a 0,00001 % shareholder, but the problem is that solidity doesn`t work with decimals so I would have to somehow normalize the shareholder % to a number between 1 - 100 to assign it to the vote weight of that contributor.

What are ways to build a weighted vote system for such DAO contracts ?