fix the SAM header parser (#377)

Author: bicycle1885

src/align/hts/sam/reader.jl

@@ -17,6 +17,7 @@ type SAMReader <: Bio.IO.AbstractReader
         reader = new(Ragel.State(samparser_start, input), SAMHeader())
         while !eof(input) && BufferedStreams.peek(input) == UInt8('@')
             # NOTE: This reads a header line, not the first record.
+            reader.state.cs = samparser_start
             @assert read(reader) == SAMRecord()
         end
         return reader