Ensure consistent icon size, allow generateIndentCSS override, fix demo

[himdel]

Fixes #49

Demo build was failing on an import, changed to a relative import,
and added normalize.css so that the demo uses the same reset stylesheet as the UI.

Added an optional callbacks.generateIndentCSS prop, a function to generate the indent css given max depth. Returning an empty string will disable css generation.

Updated css so that all icons are actually 1em + 4px wide total.

@brumik WDYT?

---

Before:

After normalize.css + border-box:

After everything:

[brumik]

This was used with npm link to show that it is imported from the package, but I guess, it is more convenient like this.

[himdel]

ah, looks like we can keep the name and use an alias, that also works :) updated

[brumik]

Thanks, I like it (except that one small thing I commented under). Can you please generate new docs for it with npm docs after you updated the comments?

[himdel]

Can you please generate new docs for it with npm docs after you updated the comments?

Well, npm docs doesn't really work, because it doesn't run it in a globstar supporting shell by default (so no **):

> [email protected] docs /home/himdel/react-wooden-tree
> typedoc --out docs --name 'React Wodden Tree' --target es6 --excludePrivate --excludeProtected --excludeExternals --mode file src/**/{Tree,types}.tsx

fs.js:114
    throw err;
    ^

Error: ENOENT: no such file or directory, stat '/home/himdel/react-wooden-tree/src/**/{Tree,types}.tsx'
    at Object.statSync (fs.js:855:3)

But running manually, with some additions worked, added :)

typedoc --out docs --name 'React Wodden Tree' --target es6 --excludePrivate --excludeProtected --excludeExternals --mode file src/**/{Tree,types}.tsx

# remove /home/himdel/react-wooden-tree references
perl -i -npe 's/.home.himdel.//' docs/**/*.*

# fix github/himdel references back to github/brumik
perl -i -npe 's#github.com/himdel#github.com/brumik#' docs/**/*.*

[himdel]

Should be ready @brumik :)