replace homegrown Error with failure crate

This reduces boilerplate, making it a bit easier for me to split the db stuff
out into its own crate.

src/cmds/config/cameras.rs

@@ -35,7 +35,7 @@ use self::cursive::traits::{Boxable, Identifiable, Finder};
 use self::cursive::views;
 use db;
 use dir;
-use error::Error;
+use failure::Error;
 use std::collections::BTreeMap;
 use std::sync::Arc;
 use stream::{self, Opener, Stream};

src/cmds/config/dirs.rs

@@ -35,7 +35,7 @@ use self::cursive::traits::{Boxable, Identifiable};
 use self::cursive::views;
 use db;
 use dir;
-use error::Error;
+use failure::Error;
 use std::cell::RefCell;
 use std::collections::BTreeMap;
 use std::rc::Rc;

src/cmds/config/mod.rs

@@ -38,7 +38,7 @@ extern crate cursive;
 use self::cursive::Cursive;
 use self::cursive::views;
 use db;
-use error::Error;
+use failure::Error;
 use regex::Regex;
 use std::sync::Arc;
 use std::fmt::Write;