conda share doesn't work in Python 3

```pytb
$conda share
An unexpected error has occurred, please consider sending the
following traceback to the conda GitHub issue tracker at:

    https://github.com/ContinuumIO/conda/issues"


Traceback (most recent call last):
  File "/Users/aaronmeurer/anaconda3/bin/conda", line 7, in <module>
    exec(compile(open(__file__).read(), __file__, 'exec'))
  File "/Users/aaronmeurer/Documents/Continuum/conda/bin/conda", line 5, in <module>
    sys.exit(main())
  File "/Users/aaronmeurer/Documents/Continuum/conda/conda/cli/main.py", line 148, in main
    args.func(args, p)
  File "/Users/aaronmeurer/Documents/Continuum/conda/conda/cli/main_share.py", line 30, in execute
    path, warnings = create_bundle(prefix)
  File "/Users/aaronmeurer/Documents/Continuum/conda/conda/builder/share.py", line 65, in create_bundle
    info, tmp_path, update_info)
  File "/Users/aaronmeurer/Documents/Continuum/conda/conda/builder/packup.py", line 188, in create_conda_pkg
    update_info(info)
  File "/Users/aaronmeurer/Documents/Continuum/conda/conda/builder/share.py", line 34, in update_info
    h.update(spec)
TypeError: Unicode-objects must be encoded before hashing
```