Fastq: no more Pull_based

Towards #69.
Sam: no more Pull_based

Towards #69.
wig_correlate: no more Pull_based

Towards #69.
lwt_tests/main.ml: no more Pull_based

Towards #69.
test_bed: no moer Pull_based

Towards #69.
test_fasta: no more Pull_based

Towards #69.
test_wig: no more Pull_based

Towards #69.
wig_correlate: use our custom Stream module
add Stream under Biocaml module
test_zip: no more Pull_based

Towards #69.
delete Transform.Pull_based

Closes #69.