Remove nativeBind usage

[jridgewell]

We cover almost all of nativeBind's cases:

• Binding function to context
• Binding function to context with args
• Binding constructor with args

The only downside is supported environments will no longer get the correct length property of the bound method. Usually, you subtract the number of bound args from func's length. But, now Underscore is consistent between all environments.

http://jsperf.com/native-bind-vs-underscore/2

Re: #2197

[michaelficarra]

I'm okay with this.

edit: By the way, we can probably have additional performance gains (and avoid inconsistent behaviour between environments for sparse arrays that @jdalton always brings up) by removing the remaining native fallbacks.

[unwitting]

Alternative in #2198 which still uses native bind and therefore would preserve arguments.length, but at massive cost compared to this approach.

See: http://jsperf.com/underscore-js-2198-vs-2199 - #2198 was twice as fast as current, but this lodash-style approach blows it out of the water.

[megawac]

This is a breaking for some constructor cases. Consider

var D = _.bind(Date, null, 2015, 05)
new D(10);

Sure this doesn't work in old environments but it may break some peoples code.

It also affects other uses such as toString

/cc @jdalton