Update to Lunr 2.0.3

[sn3p]

Closes https://github.com/manastech/middleman-search/issues/25

• [x] Update to Lunr 2.0.3
• [x] Implement new Lunr API
• [ ] Automatic minification?

After implementing the new Lunr API changes all seems fine, and the specified pages are indexed. But after refreshing search.json in the browser was empty again.

@matiasgarciaisaia maybe you have some insights on what might be the problem?

[gerwitz]

I am using this PR in production. So, hearty +1

[sn3p]

Then maybe the problem was with my setup, good to know 👍 Maybe this is production ready after all. @matiasgarciaisaia what do you think?

Before merging we might want to:

• Update to the latest Lurn version (v2.1.2 at this point).
• Decide on the minification issues (this and this).

[sn3p]

@matiasgarciaisaia would you consider minifying lunr.js manually on every update for now?

If you don't mind we can get this PR merged 💃

[westonganger]

Please merge this. Searching is severely impaired using the old version.

[tnir]

I hope someone from this Org merge this too 🙏