Initial 'Biocaml_vcf' version

Hello, I've implemented the basics of VCF4.1 [spec](http://www.1000genomes.org/wiki/Analysis/Variant%20Call%20Format/vcf-variant-call-format-version-41), so maybe you guys can take a look?

Here's what isn't supported at the moment:

* `##FORMAT` and per-sample columns,
* `##ALT`,
* `##SAMPLE`,
* `##PEDEGREE` and `##pedigreeDB`.