Replace the `server` alias with a function that optionally takes an argument specifying the port number

Inspired by @padolsey’s https://gist.github.com/1525217#gistcomment-71652.
Remove old `server` alias

Ref. 958517dcf4210aefffcafa3cc41f4ebb4edd5e36
`server`: Use parameter expansion instead of a fake ternary
README: Document the -f/--force option for bootstrap.sh
`server` function: Set the default Content-Type to `text/plain` instead of `application/octet-stream`

Hat tip to @cowboy: https://github.com/cowboy/dotfiles/blob/2874a86d207883a18e5e4c01219f9adb42d82c09/bin/serve#L26-43
README: Add Git-less installation instructions

Closes #35.
Use `tar -z` explicitly

Ref. #35.
Serve unknown file types as UTF-8, as suggested by @janmoesen
Include .vim directory and subdirectories
README: List files while untarring
Better `json` function

Ref. 9b0af44766d2a2cc61ae0142ac3ec9f0bed75674
`.osx`: Restart the `SystemUIServer` and suppress `kill` output.
Merge pull request #37 from kitcambridge/patch-1

.osx: Restart the `SystemUIServer` and suppress `kill` output
.gitignore: Add more OS-specific hidden files
`server` function: Serve everything as UTF-8

Even though this is not technically correct for binary files, it doesn’t actually break anything.
.osx: Enable iTunes track notifications in the Dock

Screenshot: http://www.maclife.com/article/howtos/5_ways_customize_dock_terminal
README: Clarify that it doesn’t matter where the repository is cloned, and document ~/.extra
README: Tweak the part about ~/.extra
.bash_prompt: Add screenshot URL
.bash_profile: Be sure to source `.bash_prompt` first, in case it sets the PATH and subsequent dotfiles rely on it