= io: optimize BackPressureHandling: keep track of length instead of calling Queue.length
= io: BackPressureHandling: make sure Acks never slip through to the pipeline
! routing: move `UserPassAuthenticator.cached` to `CachedUserPassAuthenticator.apply`, fixes #352

Because `UserPassAuthenticator.cached` relies on a spray-caching Cache even code not using this method
(but simply other `UserPassAuthenticator` methods like `apply` or `fromConfig`) must have spray-caching
on the classpath in order to avoid a `bad symbolic reference` compiler error.
This patch moves the `cached` method into a dedicated object thereby freeing up `UserPassAuthenticator`
from the dependency on the spray-caching module.
Merge pull request #353 from spray/ticket/352

routing: move `UserPassAuthenticator.cached` to `CachedUserPassAuthenticator.apply`, fixes #352
! http: make only standard charsets available as constants, fixes #340

Only standard charsets are known to be available on all Java platforms.
If another one was missing, initialization fatally aborted. Constants
for others charsets can still be retrieved from the registry but can't
be supplied as constants as those may not be available.

Another bug was fixed here: the 'ISO-8859-10' charset was wrongly registered
as 'ISO-8859-1'.
Merge pull request #354 from jrudolph/wip/fix-missing-charsets

! http: make only standard charsets available as constants, fixes #340
= can: make client connection actors actively close the connection after completion of a `Connection: close` response
= io: fix missing string interpolation in log statement
= can: remove active connection closing from HttpHostConnectionSlot (now in client connection actor)
= can: prevent `Received illegal response` warning after regular PeerClosed events, fixes #350
= io: speed up BackPressureHandlingSpec by factor of 10 (from 20s to 2s)
= can: small improvement in SprayCanServerSpec
Merge pull request #355 from mikemckibben/fix/missing_string_interpolation

fix for missing string interpolation with log statement
! routing: redefine `PathMatchers.Empty` as `PathMatchers.Neutral` with explicit type annotation, fixes #339

`Empty` is not a good name for a PathMatcher that always matches without consuming anything, as it can easily be misunderstood as a PathMatcher for `Path.empty`. We therefore rename it here to `Neutral`.
Merge pull request #332 from jrudolph/back-pressure-optimizations

Back pressure optimizations
Merge pull request #357 from spray/ticket/339

! routing: redefine `PathMatchers.Empty` as `PathMatchers.Neutral` with explicit type annotation, fixes #339
Merge pull request #356 from spray/wip/ticket-350-and-more

Fix for #350 (erroneous `Received illegal response` warning in spray-can client), smaller improvements
Added support to play-json with basic error handling.