Remove lodash dependency

[EdwardDrapkin]

Hey there,

I noticed you had done some work recently to reduce the bundle size incurred by using lodash, so I went ahead and pulled all of it out.

Here's what I did:

1. I created utils.js with IE8-compatible implementations of isFunction(), isArray() and isObject().
2. I replaced calls to _.isFunction(),_.isArray() and _.isObject() with those implementations.
3. I replaced calls to _.assign() with Object.assign() and added babel-plugin-transform-object-assign to maintain IE8 compatibility with _.assign().
4. I replaced a call to _.isUndefined(map[key]) with (!(key in map)).
5. I replaced a call to _.forEach(obj) with for(const key in obj).
6. I replaced a call to _.trim() with a trim() implementation that uses str.trim() or a regex if it's not there for IE8 support.
7. I replaced a call to _.filter() with a filterForTruthy() function.

If you don't care about IE8 support, let me know because a lot of the code here is for IE8 support.

Thanks!

[EdwardDrapkin]

I went ahead and fixed the tests so that they passed the eslint check too. The build should run fine now.

Sorry for spamming the PR with commits, my IDE was setup to use my eslint file, not yours. Oops!

[gajus]

I noticed you had done some work recently to reduce the bundle size incurred by using lodash, so I went ahead and pulled all of it out.

Please consider raising an issue prior to starting to work on a PR. As a very least, it is worth checking the existing issues/ PRs:

• https://github.com/gajus/react-css-modules/pulls?q=is%3Apr+lodash+is%3Aclosed
• https://github.com/gajus/react-css-modules/issues?q=is%3Aissue+lodash+is%3Aclosed

Closing. No intention to stop using lodash. Note, that we are only bundling the utility functions that we are using; not the entire lodash library.