Targqc

- Python 3 support

- Created bioconda package
- Add script to build Venn diagram for a set of BED files:

bed_venn.py *.bed -o res_dir

- Support custom genomes. Provide a path to indexed fasta file with `-g`:

targqc *.bam --bed target.bed -o results -g /path/to/some_genome.fa

When running from BAMs, only the `.fai` index is used, and the fasta file itself can be non-existent.
When running from fastq, bwa indexes are also required.

- Update BED file annotation package.

- BED annotation: --seq2c mode.

- Downsampling to 5% by default instead of 500k read pairs.