added compiling

COMPILING.md

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+# Compiling hgraph
+
+1.  initialize the sandbox
+		cabal sandbox init
+2.  install dependencies
+		cabal install --only-dependencies 
+3.  build package
+		cabal build
+4.  Optional build documentation (Requires haddock - installable with cabal install haddock)
+		cabal haddock
+5.  Run with
+		./hgraph input.mat input.adj weights.p +RTS -N<Number of Cores>
+	and redirect the output into desired target.