update to use liner fork

Dependencies are handled by looking for a package manifest file in the
local package database. The manifest contains all the dependencies for a
package, and a dependency graph is built from all of them. Then a
topological sort is performed and an OrderMap (linked hash map) of
package names in the order which they are to be installed in is
returned. An OrderMap is used because it preserves the order of the
packages and it has fast lookup times for checking duplicate packages.

Use BufWriter

Add --root argument; print usage on no subcommand

Fixes absolute path

Better error handling

It is short, and only used in one place.

Do not follow symlinks when creating package

Determine default target based on LLVM triple at build

Use clap for argument parsing, and allow a --target argument to choose which target to download packages for

The cookbook could be used to build for multiple architectures, if that
is ever supported.

Define TARGET environment variable for Travis