Data Structures (update)

Updated the Suffix Tree class to be more space efficient.  Instead of
storing the substring associated with each edge, we only store the start
and end indices of each substring.

Additionally, the Trie class from Rosalind Problem 054: Introduction to
Pattern Matching has been added to the data structures script.
Linguistic Complexity of a Genome

Solution to Rosalind Problem 080: Linguistic Complexity of a Genome