improve constructors and accessors.
add Trie Reader/Writer and its test.
LongsSuccinctBitVector
speed optimization.
add construtor.
add next0 method.
add trimToSize method to BitVector and next0 method to
SuccinctBitVector.
support LongsSuccinctBitVector.
add Constructor that receives String[].
change referenting class to more abstract one.
introduce nodeSize().
implement toString method.
clarify the meaning of argument.
add nodeSize.
merge TailLOUDSPPTrie to TailLOUDSTrie. refactor sbv.
fix ArrayIndexOutOfBoundException.
improve tests.
implement toString.
fix bug.
add appendBitStrings method.