.aliases: Add `week`

Thanks to @sindresorhus: https://twitter.com/sindresorhus/status/312206490880589824
.functions: Add `cdf`

`cdf` changes the working directory to the top-most Finder window location. Thanks to @sindresorhus and @paulirish!
.exports: Always enable colored `grep` output
bootstrap.sh: Pull from the master branch explicitly
.osx: Add possible values for AppleShowScrollBars

Ref. #170.
Update shebangs

If the user installs a custom Bash build, why not use it?

Ref. #196 and #198.
README: Add author field
.functions: Add `targz`

`targz some-directory` creates `some-directory.tar.gz`, where compression is handled by either `zopfli` (if available) or `gzip`.
.functions: Avoid `rm` error message in `targz` when `gzip` is used
.functions: Improve `targz`

* Only use `zopfli` when it’s available and if the `.tar` file is smaller than 50 MB.
* Use `pigz` instead of `gzip` when it’s available.
* Always exclude `.DS_Store` files when creating a tarball.

Closes #199.
bootstrap.sh: Don’t make the home directory world-readable

Fixes #159.
.brew: Install native apps through homebrew-cask

Closes #200.
.brew: Add some more applications
.osx: Update filename for Dropbox’s green checkmark icon
README: Update contributors list

Add @sindresorhus and @alrra because of their many contributions. Sort the list alphabetically.
README: Fix minor typo
pull in updates from upstream