Improve error message on blank CartoCSS in multilayer config
Add support for request profiler

Needs to be explicitly activated via config useProfiler:true
Target 0.13.0
Release 0.13.0
tweak NEWS for 0.12.10 and 0.13.0
Include renderer build time in profile
Do not console.log the profile (log_format can be used for that)

In order to print the profile in the log you can include
:res[X-Tiler-Profile] in the log_format
Prepare for 0.13.1
Avoid checking interaction-less layergroup configs multiple times
Print full layergroup config with resulting token on creation

Closes #80
Drop another explicit PROFILE log (use logger)
reworded items
Release 0.13.1
Prepare for 0.13.2
Rewrite mapnik XML parsing error to start with style name
Fix repository url in package.json
Fix author and contributors