Update Demystify to Python3.

(Requires ANTLR3 Python3 target.)
Update INSTALL and README for python3.
Merge branch 'master' into python3

Conflicts:
	demystify/demystify.py
	deps/deps.py
Merge branch 'master' into python3
2to3 the last commit.
Merge branch 'master' into python3
Merge branch 'master' into python3
Update INSTALL and README for ANTLR3.5.
Fix typo in INSTALL instructions.
Update INSTALL to reflect ANTLR 3.5 release.