Support default-server option in webrouter

Modify the webrouting service so that it defaults to using the
default server set in the webserver service configuration rather
than a server with id :default.
Test default server requirement for webrouter

Add a test to the webrouting service that ensures that a default
server is required if any endpoints are not configured with
servers
Merge pull request #55 from fpringvaldsen/webrouting-fix

Use webserver's default server in the webrouter
bump project version to 0.7.0-SNAPSHOT
lein-release plugin: preparing 0.7.0 release
lein-release plugin: bumped version from 0.7.0 to 0.7.1-SNAPSHOT for next development cycle
update CHANGELOG.md for 0.7.0 release
Add a clojars version badge to the README.md

This simplifies and automates the display of the latest version. Its a shame
its not text so it can't be cut & paste, but its better then nothing and
maintained by clojars, so no reliance on some startup SaaS service that may
disappear tomorrow.

Signed-off-by: Ken Barber <ken@bob.sh>
Add a callback to the rewriteURI method
(TK-53) Add get-route service function

Add a get-route service function to the Webrouting service which
gets the web-route configured for a service in the configuration
file.
Merge pull request #58 from fpringvaldsen/TK-53-get-route

(TK-53) Add get-route service function
Fixes based on the PR comments
Merge pull request #57 from fhrbek/rewrite_uri_callback

WIP - Add a callback to the rewriteURI method
(TK-45) Add string support to `:scheme:` option

Allow the `:scheme` option for a proxy to take a string
as well as a keyword.
(TK-33) Add proxy redirect test

Add a proxy redirect test to the proxy test file.
(TK-33) Add redirect support to proxy

Add redirect support to the proxy by setting the HTTPClient
created by Jetty to follow redirects. Add tests for this
functionality.
(TK-33) Add `:follow-redirects` proxy option

Add a `:follow-redirects` proxy option, which allows the user to
specify whether the HttpClient created by a ProxyServlet follows
redirects.
(TK-33) Explicitly set default follow redirects

Explicitly set the followRedirects setting on the HttpClient
created by a ProxyServlet in the default case. Cleanup redirect
tests.
(TK-33) Remove unused macro

Remove unused `with-target-and-proxy-servers-redirect` macro.
Merge pull request #56 from kbarber/maint/master/clojars-version-badge

Add a clojars version badge to the README.md