refactored c extensions into one

src/main.c

@@ -0,0 +1,18 @@
+#include "overviewer.h"
+
+#include <numpy/arrayobject.h>
+
+static PyMethodDef COverviewerMethods[] = {
+	{"alpha_over", alpha_over_wrap, METH_VARARGS,
+        "alpha over composite function"},
+    {"render_loop", chunk_render, METH_VARARGS,
+        "Renders stuffs"},
+    {NULL, NULL, 0, NULL}        /* Sentinel */
+};
+
+PyMODINIT_FUNC
+initc_overviewer(void)
+{
+        (void) Py_InitModule("c_overviewer", COverviewerMethods);
+        import_array();  // for numpy
+}