readme slight error

(so, the first print is incorrect)

readme has
```py
curve = Curve({0:0,2:2})

print(curve.keyframes) # prints [0, 2]
print(curve.values) # prints [0, 2]
print(curve.label) # prints something like "curve_SiF86D
```
but output is

```
SortedKeysView(SortedDict({0: Keyframe({'t': 0, 'value': 0, 'interpolation_method': 'previous'}), 2: Keyframe({'t': 2, 'value': 2, 'interpolation_method': 'previous'})}))
[0, 2]
curve_1PXGU2
```