Mod:
    Parse.java:
        Added comments

    JavaParser.java:
        Updated the genSymbols method and a private class 'NodeVisitor' which
        implements ASTVisitor.  genSymbols returns an instance of the
        Symbols class containing all relevant data about the Java code.

    JavaSymbols.java:
        Add fields which map class, interface, method, field, and
        variable names to positions.