use the read-only versions of git submodules

write-access is available for developers only

.gitmodules

@@ -1,27 +1,27 @@
 [submodule "lunit"]
 	path = lunit
-	url = git@github.com:eressea/lunit.git
+	url = git://github.com/eressea/lunit.git
 [submodule "crypto"]
 	path = crypto
-	url = git@github.com:eressea/crypto.git
+	url = git://github.com/eressea/crypto.git
 [submodule "cmake"]
 	path = cmake
-	url = git@github.com:eressea/cmake.git
+	url = git://github.com/eressea/cmake.git
 [submodule "eressea"]
 	path = eressea
-	url = git@github.com:eressea/core.git
+	url = git://github.com/eressea/core.git
 [submodule "quicklist"]
 	path = quicklist
-	url = git@github.com:badgerman/quicklist.git
+	url = git://github.com/badgerman/quicklist.git
 [submodule "critbit"]
 	path = critbit
-	url = git@github.com:badgerman/critbit.git
+	url = git://github.com/badgerman/critbit.git
 [submodule "dlmalloc"]
 	path = dlmalloc
-	url = git@github.com:badgerman/dlmalloc.git
+	url = git://github.com/badgerman/dlmalloc.git
 [submodule "cutest"]
 	path = cutest
-	url = git@github.com:badgerman/cutest.git
+	url = git://github.com/badgerman/cutest.git
 [submodule "iniparser"]
 	path = iniparser
-	url = git@github.com:badgerman/iniparser.git
+	url = git://github.com/badgerman/iniparser.git