A tiny hack in{sp,f}ect a padrino environment

This adds a small binary that allows to watch for know error conditions
and hook into certain aspects at startup time of a padrino application
to gather info.

Currently implemented is suite to detect json and yajl being loaded
concurrently.
Merge pull request #1027 from skade/padrino-perf

padrino-perf: watch out for problematic conditions in your app