Fix issue #66.

Do not test internal methods.

- Use single quotes
- No more backslashes at line end

For some cases missing EOL is expected, but diff -b will ignore EOL
difference, use cmp instead.

Optimize output

Update readme with --wrap details

Remove workarounds added while implementing --wrap, so that redundand
trailing sequences like `\x1b[32m\x1b[0m` are removed.

Also, actually run wrap regression tests; it should have been done in
the --wrap commit but somehow slipped away while addressing PR comments.

Implement --wrap flag

Which causes long lines to be nicely wrapped in side-by-side mode. To be
used primarily with `-s -w0`.

added an argument to control tab expansion

Implement pep8 check.  Excludes `E203 whitespace before ':'` for now.

Excludes E203 whitespace before ':' for now.

TODO: look into pep8 for why `# nopep8` does not work here

Added another suggested way to use cdiff with git

Diff of diff

Trying an older version

Common error of using lstrip:

 lstrip('\x00+') will eat all '+' after '\x00'

People complains lightgreen is nearly unreadable in solarized dark color
scheme.  Use green instead, which looks good enough for both