Additions and fixes to 2015/endoh3

Fixed Makefile so that make ; ./prog will work.

He provided additional source files that do different things. See the
README.md for details and how to run (try section). He said that there
should be a tarball with other source files but I don't see it and he
doesn't have a download. I'll ask him for it later.

Updated .gitignore.

2015/endoh3/.gitignore

@@ -1 +1,5 @@
 prog
+ioccc
+koch
+pi
+quine