add RunWith annotation.
Merge pull request #172 from cgruber/supportstatefulrootmodules

add RunWith annotation.
Make ObjectGraph itself an abstract type with five abstract contract methods (plus the static create()), moving the implementation into a static inner class.
Merge pull request #173 from cgruber/abstractgraph

Make ObjectGraph itself an abstract type
Use SourceVersion.latestSupported() to avoid warning with JDK 7.

When using dagger-compiler in a Java 7 project, the compiler used to issue
a "Supported source version 'RELEASE_6' from annotation processor
'dagger.internal.codegen.InjectProcessor' less than -source '1.7'" warning.
Merge commit 'c19d3828c122373b1bee62a7feb140e22f5f8e4c' into google
Merge commit '6024e62af666dd798d4122c98773ba889ca2b7ba' into google

  Use SourceVersion.latestSupported() to avoid warning with JDK 7.