indexcov: panic parsing time

[CarlosBorroto]

Seems like +00:00 is breaking the parsing of the time RG tag. Not sure if + is allowed here, I would assume it is.

$ goleft indexcov --directory goleft_output/ my.bam
panic: parsing time "2017-08-28T14:53:35.804417+00:00": extra text: +00:00: line 88: "@RG\tID:MY_SAMPLE\tSM:MY_SAMPLE\tLB:MY_SAMPLE\tPL:ILLUMINA\tPU:HNNKFAFXX-L004\tCN:GL\tDT:2017-08-28T14:53:35.804417+00:00"

goroutine 1 [running]:
github.com/brentp/goleft/indexcov.RefsFromBam(0x7fff82d67923, 0x38, 0x0, 0x0, 0x1, 0x0, 0xc42011ee10)
	/home/brentp/go/src/github.com/brentp/goleft/indexcov/indexcov.go:294 +0x509
github.com/brentp/goleft/indexcov.getReferences(0x7fff82d67914, 0xe, 0xc420120f01)
	/home/brentp/go/src/github.com/brentp/goleft/indexcov/indexcov.go:311 +0xb9
github.com/brentp/goleft/indexcov.Main()
	/home/brentp/go/src/github.com/brentp/goleft/indexcov/indexcov.go:340 +0x20e
main.main()
	/home/brentp/go/src/github.com/brentp/goleft/cmd/goleft/goleft.go:68 +0x17f