Do not read the edgelist file on the command line

Revert commit e8a607ef because now we are writing a file. We are
compelling the user to run this script in the directory containing the
input file so the output file does not get lost in the arborescence.

Analysis/read_eddy_graph.py

@@ -2,12 +2,10 @@
 
 import networkx as nx
 import csv
-import sys
 
-if len(sys.argv) != 2: sys.exit("Required argument: edgelist-CSV-file")
 G = nx.DiGraph()
 
-with open(sys.argv[1]) as f:
+with open("edgelist.csv") as f:
     reader = csv.reader(f, delimiter = " ", skipinitialspace = True)
 
     # Skip title lines: