In general great work, the core of it is ready to merge.

Just a couple of questions, check them please.
And some issues:

• use the "natural" zero value of big.Int instead of creating a new instance all the time
• I often get remarks that I comment too much, but I maintain better too much comments than too little. Generally, don't ignore return values, and if the test really can, comment why.

A small nitpick but approving.

Generally though, for future PRs, I see a lot if ignored return values in the tests. It indeed looks like they are not needed for the tests in question, which is why I approve, but it is generally a rejected practice in the project, and should be avoided whenever possible.

i've left some questions in order to better understand these changes before giving my approvial.

besides these, i'd like to ask: why did we go for a mintable ERC20 instead of a regular one?

finally: please create an issue (if there isn't one already) for the Ropsten factory update in case this is still pending.