tests/browser.migration: compare version parts as numbers not strings

[alxndrsn]

Current master implementation:

> versionGte('PouchDB v9.0.0', '8.0.0')
true
> versionGte('PouchDB v10.0.0', '8.0.0')
false

This PR implementation:

> versionGte('PouchDB v9.0.0', '8.0.0')
true
> versionGte('PouchDB v10.0.0', '8.0.0')
true

[garethbowen]

Nice catch!

Might be worth using semver, but I'll leave that up to you.

[alxndrsn]

Might be worth using semver, but I'll leave that up to you.

Possibly, but we can't just require() deps in the integration tests & I'd rather not add extra dependencies as they are currently minimal:

pouchdb/tests/integration/index.html

Lines 10 to 13 in 2dfadd1

	<script src="../../node_modules/whatwg-fetch/fetch.js"></script>
	<script src="../../node_modules/mocha/mocha.js"></script>
	<script src="../../node_modules/chai/chai.js"></script>
	<script src="../../node_modules/chai-as-promised/lib/chai-as-promised.js"></script>