Update INSTALL doc dependency information

Some changes to the INSTALL documentation dependency sections:
- Fedora 18+ now has node
- libyaml is required in forthcoming assets changes
- Formatting cleaned up
- build-essential added for Debian derivatives
Move asset definitions to YAML

In the process, I squashed some bundles together so we have fewer
scripts wherever a direct dependency is only required by one bundle.
Examples include the fuzzy text anchors, which now incorporates all
its dependencies when minified.
Remove unused import
Merge pull request #1070 from hypothesis/yaml_assets

Yaml assets