Temporary Fix in limit() when expression.is_Add is True

Please refer https://groups.google.com/forum/?fromgroups=#!topic/sympy/61pRw1PINUA

Currently,
```py
>>> from sympy import *
>>> x=Symbol('x')
>>> limit(1+(1+1/x)**x,x,oo)
2
```
Desired,
```py
>>> from sympy import *
>>> x=Symbol('x')
>>> limit(1+(1+1/x)**x,x,oo)
1 + E
```