Slight change to unit tests, docs

Unit test now creates Component with
Manager::addComponent.

src/EC/Manager.hpp

@@ -253,6 +253,8 @@ namespace EC
 
     EC::Manager must be created with a list of all used Components and all used tags.
 
+    Note that all components must have a default constructor.
+
     Example:
     \code{.cpp}
         EC::Manager<TypeList<C0, C1, C2>, TypeList<T0, T1>> manager;
@@ -349,7 +351,9 @@ namespace EC
     \code{.cpp}
         struct C0
         {
-            C0(int a, char b) : a(a), b(b)
+            // constructor is compatible as a default constructor
+            C0(int a = 0, char b = 'b') :
+            a(a), b(b)
             {}
 
             int a;

src/test/ECTest.cpp

@@ -8,6 +8,11 @@
 #include <EC/EC.hpp>
 
 struct C0 {
+    C0(int x = 0, int y = 0) :
+    x(x),
+    y(y)
+    {}
+
     int x, y;
 };
 struct C1 {
@@ -60,19 +65,13 @@ TEST(EC, Manager)
     std::size_t e0 = manager.addEntity();
     std::size_t e1 = manager.addEntity();
 
-    manager.addComponent<C0>(e0);
+    manager.addComponent<C0>(e0, 5, 5);
     manager.addComponent<C1>(e0);
 
     manager.addComponent<C0>(e1);
     manager.addComponent<C1>(e1);
     manager.addTag<T0>(e1);
 
-    {
-        auto& pos = manager.getEntityData<C0>(e0);
-        pos.x = 5;
-        pos.y = 5;
-    }
-
     {
         auto& vel = manager.getEntityData<C1>(e0);
         vel.vx = 1;