Fix compile error with --no-default-features

Fixes #283. Also, have Travis compile without default features either, so I get warned the next time I break it.

.travis.yml

@@ -8,4 +8,6 @@ rust:
   - stable
 script:
     - cargo build --verbose
-    - cargo test --verbose
+    - cargo test  --verbose
+    - cargo build --verbose --no-default-features
+    - cargo test  --verbose --no-default-features

src/fs/feature/mod.rs

@@ -10,7 +10,7 @@ pub mod git {
     use std::iter::FromIterator;
     use std::path::{Path, PathBuf};
 
-    use fs::fields;
+    use fs::fields as f;
 
 
     pub struct GitCache;
@@ -22,20 +22,12 @@ pub mod git {
     }
 
     impl GitCache {
-        pub fn get(&self, _index: &Path) -> Option<Git> {
-            panic!("Tried to query a Git cache, but Git support is disabled")
-        }
-    }
-
-    pub struct Git;
-
-    impl Git {
-        pub fn status(&self, _: &Path) -> fields::Git {
-            panic!("Tried to get a Git status, but Git support is disabled")
+        pub fn has_anything_for(&self, _index: &Path) -> bool {
+            false
         }
 
-        pub fn dir_status(&self, path: &Path) -> fields::Git {
-            self.status(path)
+        pub fn get(&self, _index: &Path, _prefix_lookup: bool) -> f::Git {
+            panic!("Tried to query a Git cache, but Git support is disabled")
         }
     }
 }