reorganize into separate crates

- taskchampion -- core implementation of a replica
 - taskchampion-cli -- command-line interface
 - taskchampion-sync-server -- server implementation (not much yet!)

taskchampion/src/lib.rs

@@ -0,0 +1,21 @@
+// TODO: remove this eventually when there's an API
+#![allow(dead_code)]
+#![allow(unused_variables)]
+
+#[macro_use]
+extern crate failure;
+
+mod errors;
+mod operation;
+mod replica;
+pub mod server;
+mod task;
+mod taskdb;
+pub mod taskstorage;
+
+pub use operation::Operation;
+pub use replica::Replica;
+pub use task::Priority;
+pub use task::Status;
+pub use task::Task;
+pub use taskdb::DB;