Multiple changes to rust-find

This includes:
  - Updating to rust-master
  - Adding `.travis.yml` and setting up CI builds to ensure it stays up to date
  - Some reformatting
  - Some `Makefile` changes
  - Removing some unsafe code and replacing with safe IO code

I've also done some performance testing, and found that the slowest spot is in `build_node_def_node_table` (`find_ast_node.rs`:1037-1053) - apparently looping over the ids and finding them in a hash table is slow!  I've tried to find a way to speed that up, but not been successful yet.