utils: Make the text wrapper more robust

Import python 2.7's textwrap module as cola.textwrap.  Teach it to honor
a "tabwidth" setting so that we can replace our implementation with it.

utils.word_wrap() now wraps each line individually.  We special-case
sign-off lines and delegate to the TextWrapper otherwise.

Signed-off-by: David Aguilar <davvid@gmail.com>
utils: Do not quote repository paths on Windows

Older versions(?) of msysgit required us to quote repository
paths when passing them to "git clone".  Modern msysgit
(or Windows 8, I do not know) no longer requires this and
does the right thing as-is.

Simplify things by removing this outdated workaround.

Signed-off-by: David Aguilar <davvid@gmail.com>