Waterpurifier: Divide properties into multiple requests (Closes: #73)

[syssi]

No description provided.

[coveralls]

Coverage increased (+0.05%) to 72.942% when pulling 4b69e2d on syssi:feature/waterpurifier-request-single-properties into 087c2a3 on rytilahti:master.

[rytilahti]

I'm wondering how it works with the javascript miio just fine, but maybe they are also splitting it in the background? Feel free to merge though 👍