support CleanCSS option

[linkesch]

Since the project is using CleanCSS for minification, it makes sense to expose cleancss option that would get passed down to new CleanCSS() so if somebody chooses to go beyond CleanCSS' default options, they can do so.

[coveralls]

Pull Request Test Coverage Report for Build 798

• 52 of 58 (89.66%) changed or added relevant lines in 6 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.3%) to 89.437%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
src/config.js	10	12	83.33%
cli.js	4	8	50.0%

Totals
Change from base Build 770:	-0.3%
Covered Lines:	590
Relevant Lines:	634

---

💛 - Coveralls

[bezoerb]

@orthes: can you add cli support, too?

And maybe it's more future proof to use the minify option so we're able to change the minifyer without changing the process.
true or options object = minify
false = no minify

[linkesch]

@bezoerb good feedback. Sure, that makes sense. I'll look into it.

[linkesch]

I rembased the branch over master, unfied cleancss with minify option, added it to CLI and added a test

[XhmikosR]

That's not a rebase FYI.

[linkesch]

@XhmikosR i did rebase it over master. good ol git rebase master. it had some merge conflict in README which i resolved and for some reason it ended up looking like this. no idea why.

[XhmikosR]

You can clearly see the merge commits. That is not a rebase.

[linkesch]

I'll create a separate PR. I don't know why this one ended up in this state