import changes directory

Importing the arrayfire module changes the working directory. For example:

```
$ python
Python 2.7.13 (default, Apr 4 2017, 08:46:44)
[GCC 4.2.1 Compatible Apple LLVM 8.0.0 (clang-800.0.42.1)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> print os.getcwd()
/private/tmp
>>> import arrayfire as af
>>> print os.getcwd()
/usr/local/Cellar/python/2.7.13/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/Resources
>>> print af.get_version()
(3, 3, 2)
```

This causes problems with any file names specified with a relative path.

I'm running on OS X 10.11 with arrayfire 3.3.2 installed with homebrew and arrayfire-python installed with pip.

I don't see any `chdir` calls in the module, so I'm not sure where the problem is.

Start by reproducing the import in the Python 2.7 macOS environment described in the issue, then trace the arrayfire import and its native initialization to find what changes the working directory. Done means importing arrayfire leaves the current directory unchanged and relative file paths continue to work.

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