Renames loadParents() and loadParents2() to loadChildToParent() and
loadReactionToInteraction()
Merge branch 'master' of https://github.com/ablucher/PGM-IL1.git
Merge branch 'master' of https://github.com/ablucher/PGM-IL1.git
Create method loadReactionsToGraph to load 
reactions from .sif file into a simple directed 
graph, vertices are genes, edges are interactions.
Edited loadVariableNodes() to create variables 
from vertices of our simple directed graph. Still 
need to edit method for parsing variable name.
Edited comments in method loadVariableNodes().