.gitconfig: add "wdiff" alias and set wordRegex to show nicer diffs
.gitconfig: change default behavior of "git push" to "upstream"

See "Git project seeks discussion on "push" change"
<http://lwn.net/Articles/487131/> for reasoning
.gitconfig: set diff.tool and merge.tool to "meld", for use in git-cola
Merge branch 'master' of github.com:sqrt/dotfiles