Add option to customise ignore_above

[jeremylynch]

As discussed in #728, 256 charters is quite restrictive and falls far short of the max of 32766 imposed by Elasticsearch.

This commit adds the ability to customize the 256 characters.

[ankane]

Thanks @mrjlynch! 👍 Code looks good. As is, the readme update seems a bit confusing/inaccurate. The limit only applies to where statements and exact matches.

[jeremylynch]

Thanks @ankane, readme is updated. Does that make it less confusing? Thanks

[jeremylynch]

Would you like me to further review the readme? Thanks @ankane

[ankane]

I'm still thinking this will lead to more confusion since it's most likely only relevant for a very small percentage of users. I'm happy to merge the code change, but think we should go without a readme update.

[jeremylynch]

Hi @ankane I have removed the readme as per your advise. Thanks

[ankane]

Great, thanks @mrjlynch 💯

[feliperaul]

@ankane First, congrats for this amazing project. I love searchkick.

As you can probably guess from #850, I spent an entire morning trying to understand why the exact same query would return hits only if a field was specified.

Looking at the source code I know think it's due to ignore_above param, which is set to 256 as default.

To be honest, I think readme should reflect this.