(PE-3047) Call shutdown-agents at end of shutdown processing

This commit adds a call to clojure.core/shutdown-agents to the end of
Trapperkeeper core's main function.  This allows agent thread pools to
start shutdown processing sooner than the default delay which would
occur in the shutdown of these pools.  This is especially useful for
allowing the JVM process running Trapperkeeper to terminate quickly when
an error has occurred during startup.
Merge pull request #145 from camlow325/maint/master/PE-3047-call-shutdown-agents-at-shutdown

(PE-3047) Call shutdown-agents at end of shutdown processing
Update README.md
update reference to latest version in README
Make test Logger return nil from logging functions.

Make the Logger used by with-test-logging and friends return nil from
functions like log/info.  This conforms to the normal logging API.
Previously, it was returning the value of its atom.
Merge pull request #146 from KevinCorcoran/test-logger-should-return-nil

Make test Logger return nil from logging functions.
Update CHANGELOG for 0.4.1
Bump version to 0.4.1 in lein example
lein-release plugin: preparing 0.4.1 release
lein-release plugin: bumped version from 0.4.1 to 0.4.2-SNAPSHOT for next development cycle
(TK-11) Make custom middlewares possible in the nrepl-service

With this change, one can enable custom middlewares for the nrep.
For example to make the LightTable nrepl connection work:
Add [lein-light-nrepl "0.0.4"] to your project dependencies.
Configure your nrepl-service like this:

[nrepl]
port = 12345
enabled = true
middlewares = [lighttable.nrepl.handler/lighttable-ops]
add test middleware to test nrepl-service middleware support
Add a test for array-based configuration, add docs

Some of our other supported config formats support arrays for the
values of the data, but it will generally be made available as
arrays of strings.  This commit adds a minor tweak so that
we will call `symbol` on these strings before using them, and
adds a test validating that this type of configuration will
work properly.

The commit also adds documentation for the new setting.
Merge pull request #1 from cprice404/feature/nrepl-middleware

Add a test for array-based configuration, add docs
Merge pull request #147 from exi/feature/nrepl-middleware

(TK-11) Make custom middlewares possible in the nrepl-service
CHANGELOG for 0.4.2 release
lein-release plugin: preparing 0.4.2 release
lein-release plugin: bumped version from 0.4.2 to 0.4.3-SNAPSHOT for next development cycle