Merge #278

278: small adjustments in the documentation r=torkleyy a=hartmut

minor changes in the specs book

book/src/02_hello_world.md

@@ -148,7 +148,7 @@ them. To execute the system, you can use `RunNow` like this:
 ```rust,ignore
 use specs::RunNow;
 
-let hello_world = HelloWorld;
+let mut hello_world = HelloWorld;
 hello_world.run_now(&world.res);
 ```
 

book/src/04_resources.md

@@ -40,9 +40,9 @@ So we can now rewrite our system:
 ```rust,ignore
 use specs::{Fetch, ReadStorage, System, WriteStorage};
 
-struct PosUpdate;
+struct UpdatePos;
 
-impl<'a> System<'a> for PosUpdate {
+impl<'a> System<'a> for UpdatePos {
     type SystemData = (Fetch<'a, DeltaTime>,
                        ReadStorage<'a, Velocity>,
                        WriteStorage<'a, Position>);

book/src/05_storages.md

@@ -59,9 +59,9 @@ than a `usize` because it consumes less RAM.
 
 ## `HashMapStorage`
 
-This should be used for components which are associated to very few entities, 
+This should be used for components which are associated to very few entities,
 because it provides a lower insertion cost and is packed together more tightly.
-You should not use it for frequently used components, because the hashing cost would definitely 
+You should not use it for frequently used components, because the hashing cost would definitely
 be noticeable.
 
 ## `NullStorage`

book/src/07_parallel_join.md

@@ -44,6 +44,8 @@ method call can be exchanged for `par_join`:
     }
 ```
 
-The `par_join` method produces a type implementing `rayon`s `ParallelIterator`
+The `par_join` method produces a type implementing [`rayon`s `ParallelIterator`][ra]
 trait which provides lots of helper methods to manipulate the iteration,
 the same way as the normal `Iterator` trait does.
+
+[ra]: https://crates.io/crates/rayon