cleanup: rename package and vendor dependencies for old go versions

Fixes #8 and begins to address deployability.

vendor/github.com/mattn/go-sqlite3/sqlite3_opt_introspect.go

@@ -0,0 +1,15 @@
+// Copyright (C) 2014 Yasuhiro Matsumoto <mattn.jp@gmail.com>.
+// Copyright (C) 2018 G.J.R. Timmer <gjr.timmer@gmail.com>.
+
+// Use of this source code is governed by an MIT-style
+// license that can be found in the LICENSE file.
+
+// +build sqlite_introspect
+
+package sqlite3
+
+/*
+#cgo CFLAGS: -DSQLITE_INTROSPECTION_PRAGMAS
+#cgo LDFLAGS: -lm
+*/
+import "C"