Use `node-pre-gyp` to automate build.

We've been following the build scheme used by node-sqlite3.  They refactored
their build scripts into the `node-pre-gyp` package.  Follow their lead.

This allows us to remove a bunch of ad-hoc scripts which were more-or-less
cut-and-pasted from sqlite3.
TEST: Release 0.1.3-pre1

Testing the automatic release build mechanism.