Using some but not all defaults

[jpoles1]

I noticed that when I tried to edit the defaults for minimum browser versions, but only wanted to change a single entry, I had to re-copy the entire version definition object over.

This is fine, if it's the intended behaviour, but we could also have it behave such that editing a single browser version will just overwrite that entry, while retaining the defaults for the other browsers. @mikemaccana any thoughts on if you'd like to make this change?

I believe the code in question lies on line 40 of index.js:

var browserSupport = options.browserSupport || DEFAULTS;

[mikemaccana]

Yep agreed that would be good. If you send a PR I'll merge it,.