Upgrade Guice dependency to 4.0-beta5.
test: New sangria-test project.
contextual: Make ContextSensitiveBinder work with requireExplicitBindings().

Same as regular toProvider() bindings, an explicit binding for the
provider is *not* required, unless to provider itself is injected
somewhere.  This is accomplished by generating a unique linked-key
binding for each ContextSensitiveProvider.
slf4j: Test best practices.
log4j: Test best practices.
lazy: Test best practices.
Merge branch 'test'