Installation issue with --editable option
Hello,

I'm trying to install pandas on Mac OS X 10.11.6 in a Django project. Pandas library is used with one of the 3rd party libraries that I am using in the project.

Since I don't want to switch to different package manager (Anakonda) just for installing pandas (I'm using pip now), in order for me to get the C files compiled, I decided to install pandas by including `--editable git+git://github.com/pydata/pandas.git@v0.18.1#egg=pandas` in the `requirements.txt` file and the library is now installed in my `src` dir and there's a symlink in my virtualenv's `site-packages` which points to it.

This gets these headers compiled, but causes many strange importing errors in pandas source code itself when it is imported by a third party library that is also installed with `--editable` mode. F. ex. file at `Users/eimantas/Desktop/Projects/WeShareSolar/mijnstroom/virtualenv/src/knmi-py/knmi/parsers.py` has this line `import pandas as pd`. And I had to edit this code block in `virtualenv/src/pandas/pandas/__init__.py` for things to work:

```
try:
    # XXX: I had to comment this out for things to work:
    # from pandas import hashtable, tslib, lib
    import hashtable, tslib, lib
except ImportError as e:  # pragma: no cover
    module = str(e).lstrip('cannot import name ')  # hack but overkill to use re
    raise ImportError("C extension: {0} not built. If you want to import "
                      "pandas from the source directory, you may need to run "
                      "'python setup.py build_ext --inplace' to build the C "
                      "extensions first.".format(module))

```

But then another importing error appears here: `virtualenv/src/pandas/pandas/core/config.py`:

```
File "/Users/eimantas/Desktop/Projects/WeShareSolar/mijnstroom/virtualenv/src/pandas/pandas/core/config.py", line 57, in <module>
    import pandas.compat as compat
AttributeError: 'module' object has no attribute 'compat'
```

What should I do to get these things fixed ? I'd love to be able to use this library with pip and Django.
