Add tutorial READMEs and fix tutorial return codes

Add README.md files for moeo/tutorial/Lesson{1-4}, smp/tutorial/Lesson{1-4},
and mo/tutorial/Lesson9 — these tutorials had no documentation.

Fix return 1 → return 0 in 28 tutorial main() functions across mo/ and
smp/ that unconditionally returned failure status.

mo/tutorial/Lesson6/adaptiveWalks.cpp

@@ -207,5 +207,5 @@ int main(int argc, char **argv)
     catch (exception& e) {
         cout << "Exception: " << e.what() << '\n';
     }
-    return 1;
+    return 0;
 }

mo/tutorial/Lesson6/autocorrelation.cpp

@@ -222,5 +222,5 @@ int main(int argc, char **argv)
     catch (exception& e) {
         cout << "Exception: " << e.what() << '\n';
     }
-    return 1;
+    return 0;
 }

mo/tutorial/Lesson6/densityOfStates.cpp

@@ -190,5 +190,5 @@ int main(int argc, char **argv)
     catch (exception& e) {
         cout << "Exception: " << e.what() << '\n';
     }
-    return 1;
+    return 0;
 }

mo/tutorial/Lesson6/fdc.cpp

@@ -188,5 +188,5 @@ int main(int argc, char **argv)
     catch (exception& e) {
         cout << "Exception: " << e.what() << '\n';
     }
-    return 1;
+    return 0;
 }

mo/tutorial/Lesson6/fitnessCloud.cpp

@@ -213,5 +213,5 @@ int main(int argc, char **argv)
     catch (exception& e) {
         cout << "Exception: " << e.what() << '\n';
     }
-    return 1;
+    return 0;
 }

mo/tutorial/Lesson6/neutralDegree.cpp

@@ -211,5 +211,5 @@ int main(int argc, char **argv)
     catch (exception& e) {
         cout << "Exception: " << e.what() << '\n';
     }
-    return 1;
+    return 0;
 }

mo/tutorial/Lesson6/neutralWalk.cpp

@@ -247,5 +247,5 @@ int main(int argc, char **argv)
     catch (exception& e) {
         cout << "Exception: " << e.what() << '\n';
     }
-    return 1;
+    return 0;
 }

mo/tutorial/Lesson6/sampling.cpp

@@ -252,5 +252,5 @@ int main(int argc, char **argv)
     catch (exception& e) {
         cout << "Exception: " << e.what() << '\n';
     }
-    return 1;
+    return 0;
 }

mo/tutorial/Lesson6/testMetropolisHasting.cpp

@@ -197,5 +197,5 @@ int main(int argc, char **argv)
     catch (exception& e) {
         cout << "Exception: " << e.what() << '\n';
     }
-    return 1;
+    return 0;
 }

mo/tutorial/Lesson6/testRandomNeutralWalk.cpp

@@ -274,5 +274,5 @@ int main(int argc, char **argv)
     catch (exception& e) {
         cout << "Exception: " << e.what() << '\n';
     }
-    return 1;
+    return 0;
 }

mo/tutorial/Lesson6/testRandomWalk.cpp

@@ -239,5 +239,5 @@ int main(int argc, char **argv)
     catch (exception& e) {
         cout << "Exception: " << e.what() << '\n';
     }
-    return 1;
+    return 0;
 }