Sequential reading for FASTA.

[alumi]

This PR adds a sequential reading function for FASTA like following.
It supports raw FASTA (.fa) and compressed FASTA (.fa.gz, .fa.bz2, etc.).

(cljam.fasta/sequential-read "path/to/fasta") => [{:name "chr1", :sequence "ATGC..."}, ...]

The function gives slightly better performance than cljam.fasta/read-sequence when reading entire file.

	Run#1	Run#2	Run#3
Sequential	25330 msecs	25258 msecs	25114 msecs
Random	40162 msecs	40287 msecs	40201 msecs

cljam.fasta/read takes more than 3 hours for the same FASTA file.

Currently, this is a blocking function running on a single thread.
It may be worth implementing async version using cljam.fasta.reader/sequential-read*.