Add basic class along with exception and attach

Signed-off-by: varun-r-mallya <varunrmallya@gmail.com>

tests/test_basic.py

@@ -3,5 +3,5 @@ import pylibbpf as m
 
 def test_main():
     assert m.__version__ == "0.0.1"
-    assert m.add(1, 2) == 3
-    assert m.subtract(1, 2) == -1
+    prog = m.BpfProgram("tests/execve2.o")
+    print(prog)