Fixing issue_295
DOC: improve docs, partially addressing issue #285
DOC: document returned object
TST: lengths are supposed to be equal, not almost equal
DOC: More docs on CA
DOC: references, notes about implementation for RDA
DOC: Link documentation of related methods.
DOC: PCoA scores. Closes issue #207
STY: whitespace
Rewording of the comment and adding a new test case for the feature added
Merge pull request #297 from josenavas/issue_295

Fixing issue_295
MAINT: Move FASTA and FASTQ formatting modules
MAINT: Add __init__.py file for format/sequences
DOC: Add rst index file for format/sequences
DOC: Add format.sequences to index.rst
BUG/MAINT/DOC: Fix problem when building docs

Update the imports of format_fastq
MAINT: Move format.sequences tests to tests
DOC: numpy-ify fasta_from_sequences docstring
TST: Fix tests to work with the new structure
TST: The is function aware of BiologicalSequence

fasta_from_sequences will now check if an identifier attribute is
present and if so it will use that as the sequence id when formatting
the sequences. The test suite was updated to reflect this.