Rename Druid-vs-redshift.md to Druid-vs-Redshift.md

links in documentation point to capitalized version. (http://druid.io/docs/0.6.10/)
Rename Druid-vs-vertica.md to Druid-vs-Vertica.md

links in documentation point to capitalized version (http://druid.io/docs/0.6.10/)
Merge pull request #310 from hkmurakami/master

fix broken links in documentation