Merge pull request #113 from bobthecow/patch-8

Update link to Lithium
Fix project name and link

The link to Wikidata was wrong, since this is a website, not the software.
Wikibase is to Wikidata what MediaWiki is to Wikipedia.
Merge pull request #114 from JeroenDeDauw/wb

Fix project name and link
Add link to PSR-4 on PSR index