Fix issue 49

holochain-gym#49
Note: This is strictly to bring the file into line with the docs (also see holochain-gym/holochain-gym.github.io#50). The functionality has not been tested.

1.basic/2.hashes/exercise/zomes/exercise/src/lib.rs

@@ -1,9 +1,5 @@
-use hdk::prelude::*;
-
-entry_defs![Book::entry_def()];
-
-#[hdk_entry(id = "book")]
-pub struct Book {
+#[derive(Serialize, Deserialize, Clone, Debug)]
+pub struct SomeExternalInput {
     title: String,
     content: String,
 }