#5 - Polishing.

Refactored issue tracker implementation into dedicated packages. Removed package tangles by moving some types around. Extracted GitHub specific properties into its own properties type reusing the Git credentials as we're talking to GitHub anyway.

Added Jackson parameter name module and enabled Java 8 parameter names to be able to get rid of the manually declared constructors for payload classes. Turned them into value objects where possible.

Original pull request: #14.

src/test/resources/application-test.properties

@@ -2,11 +2,12 @@
 logging.level.org.springframework=WARN
 logging.level.org.springframework.data.release=INFO
 logging.level.org.springframework.web.client=TRACE
+logging.level.org.springframework.http=DEBUG
 
 # Deployment
 deployment.repository-prefix=test-
 
 jira.username=dummy
 jira.password=dummy
-jira.url=http://localhost:8888
-github.api.url=http://localhost:8888
+jira.api-url=http://localhost:8888
+github.api-url=http://localhost:8888