Remove dependency on Ramda?

[markerikson]

I see that immutable-ops depends on Ramda. But, inspecting the source, it looks like only two Ramda functions are actually being used: curry and placeholder.

Would it be possible to replace those two functions with homebuilt equivalents, and remove the dependency on Ramda? It's a great library, but not everyone is using it, and I assume this would enable smaller bundle sizes.

[ahutchings]

I was just looking into bundle optimizations for my app and noticed this as well. Ramda has added the package.json sideEffects field in 0.26.0 and is now tree-shakable by webpack and rollup.

Now that that's available, we could also get the benefit of smaller builds by upgrading ramda.

@markerikson @haveyaseen are you all okay with this direction? I can put a PR together.

Edit: Oops, I see now that ramda was upgraded to 0.26 in #2. Can this be closed now?