Refactor ClassFileReader

- Remove ClassFileReadListener interface

- Create ClassInfo directly in ClassFileReader and return it
Extract ClassCollector from ClassFileReader

These two pieces are logically separated in that one is used to
do the actual reading of the class file format while the other is
used to analyse usage.
Repackage Class* sources

Moved to com.vandalsoftware.tools.classfile
Remove main() from ClassCollector

It is no longer used, needed, or desired. This class should not
be used as a standalone Java class.
Declare ACC flags constants

- Add convenience methods for a few accessFlag checks

- Rename hasSuperClass() to isSubclass()
Refactor listFiles

- Remove recursive calls

- Check isDirectory() inside listFiles() and return empty
  list when false
Fix javadoc

Use 3rd person (descriptive) not 2nd person (prescriptive)
Log stack trace

- Ignore exception in closeQuietly
Rename check() => usesClass()

Refactor duplicated code and replace with addUsages() method
Replace indexOf with last char comparison
Extract constant pool tag constants
Merge pull request #18 from jle/refactor_class_file_reader

Refactor class file reader