fix(exportXXX): bind the methods

[Haroenv]

Summary

These two errors were unnoticed, because the integration tests apparently bind everything.

Result

fixes #660

No more error about this.as._jsonRequest being undefined

[vvo]

Why not just a test-case/ https://github.com/algolia/algoliasearch-client-javascript/tree/develop/test/spec/common/client/test-cases?

[Haroenv]

Because it's not a single API call, it's more like browseAll

[vvo]

got it

[vvo]

Can you also add a return here:

algoliasearch-client-javascript/src/Index.js

Lines 671 to 674 in 58a4b2d

	return search().then(function(data) {
	if (typeof callback === 'function') {
	callback(data);
	}

This should be callback(); return;

so that you do not return the promise too (nothing major but still)