fix for iterative abacas
updated delimiter sequence

 Changed delimiter sequence from 100 N to 100 N 100 G 100 N preventing
 erronious splitting of Abacs output sequence.
 Abacas fills gaps with Ns and indicates overlapping contigs with  a
 sequence of 100 Ns.
update test data for new delimiter sequence
Merge pull request #37 from CraigPorter/iterative_abacas

Iterative abacas