Show error if can't open/create database

ChangeLog

@@ -2,6 +2,7 @@
 -----
 1. Tidy up code, thanks to Serial-ATA
 2. Update version of tag reader library, should now support ID3v2 in FLAC.
+3. Show error message if can't open, or create, database file.
 
 0.1.0
 -----

src/db.rs

@@ -51,8 +51,16 @@ pub struct Db {
 
 impl Db {
     pub fn new(path: &String) -> Self {
-        Self {
-            conn: Connection::open(path).unwrap(),
+        match Connection::open(path) {
+            Ok(conn) => {
+                Self {
+                    conn: conn,
+                }
+            }
+            Err(e) => {
+                log::error!("Failed top open/create database. {}", e);
+                process::exit(-1);
+            }
         }
     }