Argument list too long (propagation)

On some machines the following error occurs:
```
cat [list of refence fastas] > ./1311757.full.fa
make: execvp: /usr/bin/env: Argument list too long
make: *** [1311757.full.fa.complete] Error 127
```
A possible solution is to use one ``cat ref[i].fa >> node.fa`` command for each fasta file.