Instances don't know their arguments

Originally reported by: **Claudiu Popa (BitBucket: [PCManticore](http://bitbucket.org/PCManticore), GitHub: @PCManticore)**

---

```
#!python

class A:
def __init__(self, first, second):
self.first = first
self.second = second
a = A(1, 2)
a.first # infer it as 1
```

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- Bitbucket: https://bitbucket.org/logilab/astroid/issue/142