Fix bdist_wheel. Add Tag information to WHEEL dist info.

The wheel build with https://github.com/MacPython/pandas-wheels

```
# file: pandas-0.14.1.dist-info/WHEEL
Wheel-Version: 1.0
Generator: bdist_wheel (0.24.0)
Root-Is-Purelib: false
Tag: cp27-none-macosx_10_6_intel
```

Although it was renamed to `macosx_10_6_intel.macosx_10_9_intel.macosx_10_9_x86_64`, the real
tag didn't change.

This patch would fix the `Tag` like what I did in [mistune](https://github.com/lepture/mistune)

```
# file: mistune-0.4.dist-info/WHEEL
Wheel-Version: 1.0
Generator: bdist_wheel (0.24.0)
Root-Is-Purelib: false
Tag: cp27-none-macosx_10_6_intel
Tag: cp27-none-macosx_10_9_intel
Tag: cp27-none-macosx_10_9_x86_64
```

Related: http://lepture.com/en/2014/python-on-a-hard-wheel