Rename 'analyzer' to 'redundantcss'

[peterbe]

The original prototype only had 1 plugin and it became named as "analyzer" because the intention was for the whole project/repo to all be about finding redundant CSS selectors.

Instead we want a plugin architecture where each plugin focuses on totally different objectives. E.g. HTML validation, CSS selectors, Accessibility, etc.

I suggest we rename it to: redundantcss