Remove generated subs, use more Package::Stash
Remove runtime switching
Remove references to things that are gone
Update README and Changes
Tidy, Critic, Docs
v0.2.0

 [!Major]
 - runtime_switchable feature removed in favour of more general purpose
   code, that is performant even *with* runtime switchability being on by
   default.
 - Class methods starting with full_ removed as they're no longer used.
 - Additionally, loading `Readonly` to implement above feaures usually
   costed more than it saved.
 - Internals changes now means that only ~90 statements are required to
   execute during ->import() whereas previously it was more like ~500
   statements.

 [Dependencies::Added / runtime requires]
 - Package::Stash

 [Dependencies::Added / test requires]
 - Capture::Tiny
 - blib

 [Dependencies::Changed / build requires]
 - Module::Build 0.4005 → 0.4007

 [Dependencies::Changed / configure requires]
 - Module::Build 0.4005 → 0.4007

 [Dependencies::Changed / develop suggests]
 - Dist::Zilla::PluginBundle::Author::KENTNL v1.7.4 → v1.8.0

 [Dependencies::Removed / runtime requires]
 - B
 - Readonly
 - Scalar::Util

 [Dependencies::Removed / test requires]
 - File::Find
 - File::Temp

 [Internals]
 - Package stash mangling now done by Package::Stash
 - '_has' attribute generator removed in favor of hand-inlined methods,
   which is easier to profile and debug.