feat(iter): More relevant name for set predicates

`set` was an implementaton detail of only some of these predicates that
test against collections of data.  The collections can be unordered,
ordered, or hashed.

This also opens the door for more `iter` predicates.

BREAKING CHANGE: `predicates::set` -> `predicates::iter`.

Author: epage

src/set.rs renamed to src/iter.rs

@@ -102,7 +102,7 @@ pub use boxed::BoxPredicate;
 pub mod constant;
 pub mod function;
 pub mod ord;
-pub mod set;
+pub mod iter;
 
 // combinators
 pub mod boolean;

src/lib.rs

@@ -16,7 +16,7 @@ pub mod predicate {
     pub use constant::{always, never};
     pub use function::function;
     pub use ord::{eq, ge, gt, le, lt, ne};
-    pub use set::{contains, contains_hashable, contains_ord};
+    pub use iter::{contains, contains_hashable, contains_ord};
 
     /// `str` Predicate factories
     ///