more missing dependencies in doc/install/installation.md
Created by: blobhouse
Various required libraries are not mentioned, which cause the gem bundle step to fail. The step is slow, and you have to run it in order to see the failed dep, so really it would be great to add a line in step 1 about these libs:
libyaml libxml2 libxslt libicu
... some of which want to be compiled into Ruby in step 2.