Biostructmap

* Add faster implementation of common population stats that previously used DendroPy implementation.
* Add warning when uncertain base pairs are used with population stats.
* Fix minor bugs with loading/using multiple sequence alignments from raw Fasta format.

v0.3.0, 2018-11-29 -- Improved Memory Management. Added tools for protein sequence alignments.
* Add ability to use protein multiple sequence alignments as input data. Useful for Shannon Entropy calculation.
* Improve memory management when calculating nearby residues. No longer creates a Euclidean distance matrix, but uses a KDTree instead.

* Added ability to calculate Shannon entropy for each position in a structure using a multiple sequence alignment.

v0.2.3, 2017-10-26 -- Add scipy distance calculation back in as an option if scipy present.
* Added scipy distance calculation back. Numpy implementation was a memory hog, so will use scipy if present.

* Removed SciPy dependency, which simplifies install process.
* DSSP is only called if it is required, for example when there is a need to calculate secondary structure or solvent accessibility.
* Also removed redundant methods for writing output data to file.
* Updated README to reflect optional requirements for BLAST+, Exonerate and DSSP.

v0.2.0, 2017-10-24 -- Major update, first release since making biostructmap public.
* Added features:
* Additional genetic tests (Watterson's theta, nucleotide diversity)
* Added multi-chain support. This allows mapping of data from different chains.
* Some code refactoring was performed. map method is now available from the Structure class, not each individual Chain.
* Data requirements altered slightly. Each data object should be associated with a particular set of structure chains e.g. {('A', 'B'): data_1, ('C',): data_2}
* Reference sequences should be provided for each chain: {'A': seq_1, 'B': seq_1, 'C': seq_2}