GSComponent.transformation written incorrectly

```
>>> from glyphsLib import GSComponent
>>> foo = GSComponent("test")
>>> foo.transform = (1.0, 0.0, 0.0, 1.0, 5.0, 0.0)
>>> from glyphsLib.writer import dumps
>>> dumps(foo)
'{\nname = test;\ntransform = "(1.0, 0.0, 0.0, 1.0, 5.0, 0.0)";\n}\n'
```

Glyphs won't read this in properly; it expects this format (curly braces):

```
{
alignment = -1;
name = acutecomb;
transform = "{1, 0, 0, 1, 189, 286}";
}
```

Start with GSComponent and glyphsLib.writer.dumps, using the reproduction in the issue to trace how the transform tuple is serialized. Compare the emitted transform with the curly-brace format Glyphs expects, then verify that dumps produces readable component data in that format.

Written by the indexing model from the issue text.