"bar" documentation not found if imported as "from foo import bar"

When modules are imported as `from foo import bar` the plugin fails to find the documentation of `bar`. 
For instance, `<leader>pw` on `bar` in the following code will result in `no Python documentation found`:

``` python
from foo import bar

my_var = bar(my_args)
```

while `<leader>pW` on `bar` in the following code works as expected:

``` python
import foo.bar

my_var = foo.bar(my_args)
```
