(PE-2650) add add-context-handler function

This commit adds the add-context-handler function which is used
by trapperkeeper-ruby to register rack based ruby applications
with the webserver service.
When the function is called with only the base-path and context-paths
parameters it creates a context handler capable of serving just the
static content from the base-path location. To turn the created context
to anything more advanced one has to supply one or more objects
implementing the ServletContextListener interface which can then
customize the context handler by setting its init parameters, and by
adding servlets, filters and other listeners to it.
Additionally the commit factors out a piece of common code for registering
newly created context handlers with the webserver-context from all the
add-*-handler functions into a separate function - add-handler - to prevent
code duplication.
(PE-2650) tests for add-context-handler function

This commit adds tests for the add-context-handler function.
While at it, the structure of an existing test is changed
to be in line with all the other tests.
(PE-2650) bootstrap-services-with-cli-data -> with-app-with-cli-data

This commit updates the tests to use the safer with-app-with-cli-data
function for booting a TK service to be tested instead of the older
bootstrap-services-with-cli-data.
As the new function does a better job at setting up/tearing down the test
environment it was also possible to simplify the tests and while at it
some unused imports/requires were removed.
Merge pull request #9 from mruzicka/PE-2650_trapperkeeper_ruby_prerequisites

(PE-2650) add add-context-handler function
Move 0.3.4 changelog notes to top of file
Add changelog notes for 0.3.5 release
Merge pull request #12 from cprice404/maint/master/CHANGELOG-for-0.3.5

Maint/master/changelog for 0.3.5
lein-release plugin: preparing 0.3.5 release
lein-release plugin: bumped version from 0.3.5 to 0.3.6-SNAPSHOT for next development cycle
(PE-2650) update README.md

This commit adds descriptions of the fucntions recently added to the
WebserverService protocol to the README.md file.
Merge pull request #13 from mruzicka/PE-2650_doc_update

(PE-2650) update README.md
Update test-utils.md
Update test-utils.md
Update test-utils.md
Add support for using Jetty ProxyServlet

This commit adds a function called `add-proxy-route`, which can
be used to configure certain paths to be proxied to other hosts.
Refactor proxy tests

This commit introduces a macro to simplify the proxy tests; this
will allow us to write several more tests w/o duplicating all
of the proxy setup code.
Add support for HTTPS when proxying
Add support for specifying scheme and ssl config for proxy target

This commit adds some additional fields that you can specify
when configuring a proxy target; specifically, you may now
include a `:scheme` to force http or https (rather than using
the scheme of the original request).  You can also specify
an `:ssl-config` map, to specify the pem files to use for
the ssl context.
Add docs for new `add-proxy-route` function
Add a few more tests, cleanup based on PR feedback