Ethplorer account bug with rates not being recognized as Doubles

[wolffan]

What is the current behavior?
You can't add an ERC20 compatible wallet
Actual problem is that ethplore api changed and now rate is a string, not a number

If the current behavior is a bug, please provide the steps to reproduce starting from "launch Balance". If possible, please include a screenshot or a video.
add a wallet that contains 0.something as rate

What is the expected behavior?
Should be able to add any ERC20 wallet

Which version of Balance is affected by this issue? Did this work in previous versions of Balance?
Current master

[wolffan]

working pr with updated json models for tests if someone wants to chip in: https://github.com/balancemymoney/balance-open/pull/191

[wolffan]

PR of the fix https://github.com/balancemymoney/balance-open/pull/191