Reduced object allocation per request

Ruby Object allocation is rather slow, have searched for the "fast path"
and for Objects which are used in nearly every call and constantized
them.
add missing Constants include
added missing constantization
fix typo
move constants to webmachine namespace
don't freeze the frozen
add memory test [no ci]
let it run multiple times [ci skip]
improve header lookup time
Merge branch 'master' into less-object-allocations
Merge pull request #197 from seancribbs/less-object-allocations

Reduced object allocation per request