Start the conda config command
Add a basic conda config command

So far the options are to let you choose the file, get, which prints the
current options, and add, which writes out the given options.  There is
currently an issue where add writes out in pyyaml's preferred format, which
generally looks nothing like the user inputted format, and, even worse, clears
all comments from the config file.
Add a note
Start writing a basic yaml parser that preserves structure and comments

For now, it requires the condarc file to look like

key:
  - value

with exactly 2 spaces before "- value".
Some work on conda config
Add force option to conda config
Merge pull request #204 from asmeurer/config-command

This is #127 but only with the conda config command