Minimum Node.js version to develop

Hi there, this is a really nice project! I was setting this up locally and noticed you have the minimum Node.js version set in `package.json`. Just curious, is there any particular reason this has been set? If not, I think it will be easier for others to develop locally if this is less restrictive.

(Yarn wasn't allowing me to install the `node_modules` without switching the Node.js version.)

https://github.com/brumm/tako/blob/e981f7845960def9fd6ead2870518742be32bd65/package.json#L7-L9

Start with package.json lines 7-9 and inspect the project's Node.js setup requirements. Check whether Yarn can install dependencies with the intended supported Node.js version. Done means the development requirement is appropriate and dependency installation works without an unnecessary version switch.

Written by the indexing model from the issue text.