add script for illustrating scripting

source/_static/code/scripting.py

+from subprocess import Popen, PIPE
+
+   
+cmd = 'clustalw -align -infile={0} -output=FASTA -outfile=alignement.fa'.format('../data/abcd.fasta')
+clustal_process = Popen(cmd, shell = True, stdout = PIPE, stderr = PIPE)
+stdout, stderr = clustal_process.communicate()
+
+return_code = clustal_process.poll()
+if return_code != 0 :
+    raise RuntimeError("something goes wrong with clustalw :"+stderr)
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