do not require a sequence input
implement output buffering for GtGFF3Visitor
cosmetics
add script to check line-sortedness of GFF files
add first linesorted GFF3 out stream
add support for FASTA width and -retainids
resolve sorting
move linesorting check script to testdata directory
add testcases for -sortlines
ensure sorting by seqid and coords
gtlua: implement feature_node:{add,set,remove}_attribute()
Merge pull request #366 from satta/lua_attributes

gtlua: implement feature_node:{add,set,remove}_attribute()
Merge pull request #362 from satta/no_mandatory_seqfile_speck

do not require a sequence input
Merge pull request #364 from satta/sorted_gff3

Implement line-based sorting of GFF3 output