Fix setup

Installing from PyPI doesn't work:

```
Downloading/unpacking widgy==0.1.0 (from -r requirements.txt (line 13))
  Downloading widgy-0.1.0.tar.gz (1.3MB): 1.3MB downloaded
  Running setup.py egg_info for package widgy
    Traceback (most recent call last):
      File "<string>", line 16, in <module>
      File "/XXXX/build/widgy/setup.py", line 54, in <module>
        long_description=read('README.rst') + '\n\n' + read('CHANGELOG.rst'),
      File "/XXXX/build/widgy/setup.py", line 12, in read
        return open(os.path.join(os.path.dirname(__file__), fname)).read()
    IOError: [Errno 2] No such file or directory: '/XXXX/build/widgy/CHANGELOG.rst'
    Complete output from command python setup.py egg_info:
    Traceback (most recent call last):

  File "<string>", line 16, in <module>

  File "/XXXX/build/widgy/setup.py", line 54, in <module>

    long_description=read('README.rst') + '\n\n' + read('CHANGELOG.rst'),

  File "/XXXX/build/widgy/setup.py", line 12, in read

    return open(os.path.join(os.path.dirname(__file__), fname)).read()

IOError: [Errno 2] No such file or directory: '/XXXX/build/widgy/CHANGELOG.rst'
```

This commit adds `CHANGELOG.rst` into the dist file and also fills out some of the missing fields in the setup file.