Docs: Fix 'lintinging' typo and ref links

The [about page][1] currently renders 'Code lintinging)' (adds an extra `)`), so
switch to reference links (including npm for consistency).

[1]: http://eslint.org/docs/about/
Merge pull request #1071 from tlvince/refactor/about-typo

Docs: Fix 'lintinging' typo and ref links