Replace lodash dependency with more specific modules

[pdehaan]

I noticed that we're including all of lodash, as well as dependencies for lodash.debounce and lodash.throttle.

$ grep -irnl "from 'lodash" . --exclude-dir=node_modules

WHERE	WHAT
./src/adapters/recommended_adapter.js:2	import debounce from 'lodash.debounce';
./src/adapters/search_suggestions_adapter.js:2	import _c from 'lodash/collection'; ... _c.collect(...)
./src/views/base_view.js:3	import flatten from 'lodash/array/flatten';
./src/views/base_view.js:4	import invoke from 'lodash/collection/invoke';
./src/views/index_view.js:13	import throttle from 'lodash.throttle';

I think we can probably remove the lodash dependency switch to the following smaller modules:

• lodash/collection/collect to lodash.map
• lodash/array/flatten to lodash.flatten
• lodash/collection/invoke to lodash.invoke

[jaredhirsch]

PRs welcome. I'd much rather just include all of lodash, because nobody cares about 10 extra KB.