Replace try! macro with '?' operator.

Building with 'cargo build -vv' complains about `try!` being deprecated.
Replace with functionally-identical '?' operator.

build.rs

@@ -135,7 +135,7 @@ impl Version {
             }
             num.push(c);
         }
-        let major = try!(num.parse::<u32>().map_err(|e| e.to_string()));
+        let major = num.parse::<u32>().map_err(|e| e.to_string())?;
 
         num.clear();
         for c in parts[1].chars() {
@@ -144,7 +144,7 @@ impl Version {
             }
             num.push(c);
         }
-        let minor = try!(num.parse::<u32>().map_err(|e| e.to_string()));
+        let minor = num.parse::<u32>().map_err(|e| e.to_string())?;
 
         num.clear();
         for c in parts[2].chars() {
@@ -153,7 +153,7 @@ impl Version {
             }
             num.push(c);
         }
-        let patch = try!(num.parse::<u32>().map_err(|e| e.to_string()));
+        let patch = num.parse::<u32>().map_err(|e| e.to_string())?;
 
         Ok(Version {
             major: major,