Allow testing/example with no features (#85)

examples/hash.rs

@@ -1,9 +1,14 @@
 extern crate bcrypt;
 
+#[cfg(any(feature = "alloc", feature = "std"))]
 use bcrypt::{hash, verify, DEFAULT_COST};
 
+#[cfg(any(feature = "alloc", feature = "std"))]
 fn main() {
     let hashed = hash("hunter2", DEFAULT_COST).unwrap();
     let valid = verify("hunter2", &hashed).unwrap();
     println!("{:?}", valid);
 }
+
+#[cfg(not(any(feature = "alloc", feature = "std")))]
+fn main() {}

src/lib.rs

@@ -219,7 +219,7 @@ pub fn verify<P: AsRef<[u8]>>(password: P, hash: &str) -> BcryptResult<bool> {
     Ok(source_decoded.ct_eq(&generated_decoded).into())
 }
 
-#[cfg(test)]
+#[cfg(all(test, any(feature = "alloc", feature = "std")))]
 mod tests {
     use super::{
         _hash_password,