Fix external links in Scaladocs.

This addresses issue #41, by just taking the path of least
resistance and just entering explicit URLs for the three
external references we currently have.
Return false for timed-out `isOnline` calls

There's an ask involved in resolving isOnline, which, though it seems
unlikely, could possibly time out. If this happens, we don't want that
AskTimeout exception to escape and blow things up. So, call a timeout
"false", and let the polling take care of the rest.
Updated external documentation links.

* Link specifically to Akka 2.2.1 apidocs for Agent.
* Point to Akka 2.2.1 configuration docs, which are more useful than
  the (nonexistent in 2.2.1) NettySSLSupport class's apidocs. :)
Add better timeout test
Do not send out-of-order events to StateSupervisor

PaxosStateBridge was erroneously sending unhelpful events to the
StateSupervisor, due to a nextSeq bookkeeping bug. They were dropped
correctly, which is nice, but there were lots of errors, and some extra
work being done. This fixes that error.
Merge pull request #82 from comcast-jonm/scaladoc-warnings

Fix external links in Scaladocs.
Merge pull request #88 from clinedome-work/goodbye-badnewsbears

Do not send out-of-order events to StateSupervisor
Merge pull request #87 from clinedome-work/isonline-timeouts

Return false for timed-out `isOnline` calls
Augment MembershipActor monitoring

Add monitor hooks for current cluster.config membership, paths in the
last resolution attempt, time since last resolution attempt, and the
number of resolution failures the actor has encountered.
Merge pull request #91 from clinedome-work/membership-monitoring

Augment MembershipActor monitoring
De-stringify non-string config values

Fetch these values from config with the appropriate types. They must be
set with these types in the configuration. Indicate the necessary type
in the SiriusConfiguration object documentation.
Make .getProp work with common convertible types

Using the fancy new TypeTag, we can examine the type we get in to some
degree and add logic. This isn't pretty, but it does seem to work very
nicely, and it should make the "unstring-config" PR
backwards-compatible.