throw OutBamFile::error from OutBamFile::write(const BamRead& read)

[Peter]

From BamFile?.cc:

// FIXME if wanted perhaps we should throw an OutBamFile::error
// instead that can hold \a read

[Peter]

(In [3162]) refs #778. samwrite returns -1 if file is closed, so correct code to detect when this happens.

[Peter]

(In [3166]) throw OutBamFile::error when OutBamFile::write fails. closes #778