Python 3

Would you be interested in a patch for Python 3 support? (I prefer a pure python solution)

```py
> python -m pip install --user -e .
Obtaining file:///home/jayvdb/projects/yaml/yq
Complete output from command python setup.py egg_info:
Traceback (most recent call last):
File "", line 1, in
File "/home/jayvdb/projects/yaml/yq/setup.py", line 4, in
from itertools import imap, ifilter
ImportError: cannot import name 'imap'

----------------------------------------
Command "python setup.py egg_info" failed with error code 1 in /home/jayvdb/projects/yaml/yq/
```

The issue shows a Python 2 import error in setup.py line 4. Start by examining the setup.py file and the codebase to identify Python 2-specific syntax and libraries (like itertools.imap). Look for other files that may need updating for Python 3 compatibility. Test the installation and basic functionality after changes to ensure the tool works in Python 3.

Escrita pelo modelo de indexação a partir do texto da issue.