Change order of arguments

[gr2m]

I’d like to put secret first, that we can easily expose a calculateSessionId(username, salt, timestamp) method with

calculateSessionId = require('couchdb-calculate-session-id').bind(null, 'secret')

I think that order makes also more sense in terms of grade of security

[marten-de-vries]

The order doesn't matter for pouchdb-auth, it's something I would need to look up in the docs every time anyway. So feel free to use whatever order makes the most sense to you. :)

[gr2m]

Started a PR here: #8

@janl @boennemann @christophwitzko any reason against putting secret first?