update specs2 2.3.12
Fixed OAuth request body signing

Fixes #2899.

In Scala, it was a regression. In Java, I don't think it was ever
implemented.

I've implemented tests.

The WSRequest API in both Scala/Java needs to be merged into
WSRequestHolder, the only place it's used is by a signer (and the only
implementation is oauth, and it's not likely that there will ever be
another implementation).

So the changes I've made to WSRequest in both Scala and Java both look
like they break things, but they are in fact actually quite benign.

Long term, we should merge WSRequestHolder into WSRequest, and make it
all immutable.
Merge pull request #2899 from jroper/2899-oauth-request-body-signing

OAuth request body signing broken
Fixed a bunch of typos in the dist documentation
Issue #2907 - Show imports for Akka sample code
Catch more errors to detect when JNotify fails to load

Fixes #2831

I list the the exceptions we want to catch rather than just catching
Throwable. That's because Throwable matches  a lot of stuff we don't
really want to catch, e.g. OutOfMemoryError.
Minor change to stop a compiler warning
Merge pull request #2906 from pschichtel/patch-1

Fixed a bunch of typos in the dist documentation
Update to twirl 1.0.0-RC3
Merge pull request #2909 from richdougherty/jnotify-catch

Catch more errors to detect when JNotify fails to load
Merge pull request #2910 from pvlugter/twirl-rc3

Update to twirl 1.0.0-RC3
Merge pull request #2908 from kipsigman/2907-akka-docs

Issue #2907 - Show imports for Akka sample code
Merge pull request #2834 from xuwei-k/update-specs2

update specs2 2.3.12
Changes for some RC3 components.