When JUnit tests have assumption failures, treat them as "skipped"

JUnit has a conception of "assumptions", when encode conditions in which a test is meaningful.
When an assumption fails, it means that the test provides no useful information, and should
"halt and be ignored".  Prior to this change, Gradle was treating JUnit tests with assumption
failures as "passed".

http://junit.sourceforge.net/javadoc/org/junit/Assume.html
Add unit test coverage for JUnit assumption handling
Add integration test coverage for JUnit assumption handling
Made notify-send notifications transient so that they don't clutter notification panel in Gnome Shell
Fixed typo in javadocs.
Added Test.binResultsDir property to DSL reference.
Added some user guide material for the TestReport task type.
Mention new TestReport task type in the release notes.
Mention the 'maven-publish' plugin
mention --configuration option of dependencies task in release notes
mention --configuration option of dependencies task in user guide
mention GRADLE-2526 as potential breaking change in release notes
Treat any exception encountered when testing whether we can reach services.gradle.org as indication that we can't.
Changed the order of the features. Updated the wording in some places.
Fixed line-length issues in release notes
Rework the release notes functional test to deal with the ajax more reliably.
First draft on the release notes preamble.
Wrap lines in release notes
Reworked release notes preamble
More release notes cleanup:
- Fixed all links
- Minor content edits