Updating docs for pre-masking.
deduplicate_sequences.py can read and write gzip and bz2-compressed files
CHANGELOG
Merge branch 'origin/324-deduplicate-seqs-compression' into dev

Closes #324
Support gzip-compressed alignment files

e.g. `pplacer -c vaginal_16s.refpkg src/p4z1r36.fasta.gz` generates
p4z1r36.jplace
Support reading compressed .jplace files
Support writing compressed .jplace files

checked via:

    pplacer -p -c vaginal_16s.refpkg src/p4z1r36.fasta.gz -o test.jplace.gz
Remove duplicate function chop_suffix_if_present

Same as Ppatteries.safe_chop_suffix
Merge pull request #323 from matsen/323-compressed-alignment-files

read compressed alignment files?
CHANGELOG
CHANGELOG in docs

Mostly reformatting CHANGELOG as .rst
Merge branch 'dev' into 318-placement-specific-mask