Update dependencies

- Update retext-visit, retext, mocha, eslint;
- Remove retext from peer-dependencies;
- Add retext-content as a dev-dependency.
Refactor spec

Includes changes for retext@0.2.0
Remove testling
Update copyright in Readme.md
Fix property order in component.json, package.json
Add bower.json
Update Installation in docs

- Add Bower as an installation method;
- Rename Component.js > Component;
- Fix casing of NPM > npm.
Update .gitignore, .npmignore
Remove browser test
Remove `npm update` from travis
Add npm deployment to travis
Refactor API
Refactor Readme.md
Update changelog for 0.1.2
0.1.2