Trying to replace GtResetSourceStream with GtSetSourceVisitor/GtVisitorStream
fix some problems with set source visitor
don't test bitpackstring with array length 0

fixes issue #44
Restored original test order
Merge pull request #45 from Garonenur/dw

don't test bitpackstring with array length 0
Merge pull request #46 from standage/master

Replacing GtResetSourceStream with GtSetSourceVisitor