remove unused declaration
refactoring PackageNames use Iterables.concat()
rename
add @NonNull annotation
refactoring Constraints.Builder use ImmutableSortedSet
extract Constraints.Builder#add(Constraint)
Merge remote-tracking branch 'origin/master'

Conflicts:
	src/main/java/checkdep/util/CollectionBase.java
	src/main/java/checkdep/value/constraint/Constraints.java
	src/main/java/checkdep/value/depend/PackageNames.java