Prepare version 0.7.4
Add a bit more context to changelog
Move bootstrapping into Env::Bootstrap

* Do not mix concerns of domain with building an object graph concerning
  the domains execution environment
* Removes the amount of clutter in Env (mostly a cleanup for tracing
  where Env will grow a bit)
Fix corpus test not to assume devtools
Factor out test selection into Mutant::Selector objects

* Overall easier to test
* Reduces the need to pass around config to subjects
* Reduces the diff to tracing branch
Merge branch 'selection-environment'
Fix spelling of local variable names
[WIP] Implement line tracing for spec selection