Make GitLab.com fast

This is a joint effort of operations and development.

We're working on #42 (closed) on making GitLab.com faster in the short term and we'll add a CDN in #75 (closed)

Currently our 99% request response time is more than 5 seconds #42 (comment 4606876)

By the dates below 99% of GitLab http(s) requests will take less than the mentioned time:

• under 2 seconds at the end of 2016
• under 1 second at the end of 2017
• under 500ms at the end of 2018