Py3 fixes to lib/color_compliment.py

[ceholden]

PR fixes three bugs identified when using --colorized-hostname with Python3. I don't have confirmation yet, but this likely addresses issue #216. I used try/except blocks and version checks to be conservative and ensure this doesn't break for anyone on a very old Python 2 version, but this was probably excessive and isn't something I would have done on my own project. I'd be happy to remove them if there are concerns about the overhead.

With these changes made, I've had no problems on Python 2.6.6, 2.7.10, and 3.5.1.

Issue 1 fixed in ceholden/powerline-shell@1f1acb81cba48e35820c4a88b4c39ab5ff40db42:

Traceback (most recent call last):
  File "/home/ceholden/.homesick/repos/dotfiles/powerline-shell/powerline-shell.py", line 272, in <module>
    add_hostname_segment()
  File "/home/ceholden/.homesick/repos/dotfiles/powerline-shell/powerline-shell.py", line 251, in add_hostname_segment
    from lib.color_compliment import stringToHashToColorAndOpposite
  File "/home/ceholden/.homesick/repos/dotfiles/powerline-shell/lib/color_compliment.py", line 3, in <module>
    from colortrans import *
ImportError: No module named 'colortrans'

Issue 2 fixed in ceholden/powerline-shell@c07c4be6b4e410a56bc95284bb553f5b1baaa7f7:

$HOME/.homesick/repos/dotfiles/powerline-shell/powerline-shell.py --cwd-only --colorize-hostname
Traceback (most recent call last):
  File "/home/ceholden/.homesick/repos/dotfiles/powerline-shell/powerline-shell.py", line 272, in <module>
    add_hostname_segment()
  File "/home/ceholden/.homesick/repos/dotfiles/powerline-shell/powerline-shell.py", line 255, in add_hostname_segment
    FG, BG = stringToHashToColorAndOpposite(hostname)
  File "/home/ceholden/.homesick/repos/dotfiles/powerline-shell/lib/color_compliment.py", line 35, in stringToHashToColorAndOpposite
    string = md5(string).hexdigest()[:6] # get a random color
TypeError: Unicode-objects must be encoded before hashing

Issue 3, previously mentioned but not merged in #82, fixed in ceholden/powerline-shell@6bef8fab1dc86739f6073d8dfbacc1fb20dc1edc:

Traceback (most recent call last):
  File "/home/ceholden/.homesick/repos/dotfiles/powerline-shell/powerline-shell.py", line 272, in <module>
    add_hostname_segment()
  File "/home/ceholden/.homesick/repos/dotfiles/powerline-shell/powerline-shell.py", line 251, in add_hostname_segment
    from lib.color_compliment import stringToHashToColorAndOpposite
  File "/home/ceholden/.homesick/repos/dotfiles/powerline-shell/lib/color_compliment.py", line 5, in <module>
    from md5 import md5
ImportError: No module named 'md5

[b-ryan]

Thanks @ceholden! I would share your preference to not support older versions of Python. I haven't seen any issues where people have complained about issues in older versions.

I'm gonna merge this anyway though. The backwards compatibility isn't hurting anything.