Builder always uses zap v11

[mschoch]

No matter what configuration you pass in, zap v11 is used due to a bug:

https://github.com/blevesearch/bleve/blob/master/index/scorch/builder.go#L109-L111

[mschoch]

cc @tylerkovacs

[mschoch]

Note: if you happen to parse your config from JSON, it still may not work until this PR is merged: #1401

[mschoch]

With the bug fixes, plus the new versions of zap, I see the following sizes using the IndexBuilder with the 1 million wikipedia articles (no stored fields, no term vectors)

9083488	bleve-builder-scorch-zapv11-mil.bleve
3127756	bleve-builder-scorch-zapv12-mil.bleve
3100816	bleve-builder-scorch-zapv13-mil.bleve
3056260	bleve-builder-scorch-zapv14-mil.bleve

Essentially everything after zap v11 is just a minor improvement (for this index mapping).