Add some additional documentation.

Following suggestions in
#31 (comment)

Author: teymour-aldridge

fuzzcheck/src/builder.rs

@@ -450,6 +450,11 @@ where
     }
 
     #[no_coverage]
+    /// Uses the default sensor and pool. For most cases this is desirable, but
+    /// sometimes you might want to instead use
+    /// [`FuzzerBuilder3::sensor_and_pool`]. This is especially true because the
+    /// default sensor and pool tries to find test cases which take a long time
+    /// to execute - this slows down the fuzzer.
     pub fn default_sensor_and_pool(
         self,
     ) -> FuzzerBuilder4<F, M, V, DiverseAndMaxHitsSensor, BasicAndDiverseAndMaxHitsPool> {

fuzzcheck/src/mutators/map.rs

@@ -3,6 +3,14 @@ use std::marker::PhantomData;
 
 use crate::Mutator;
 
+/// [`MapMutator`] provides a way to transform a mutator outputting values of
+/// type `From` into a mutator outputting values of type `To`, provided that a
+/// mutator for values of type `To` exists, and it is possible to convert from
+/// `From` to `To`.
+///
+/// If you are trying to _add_ additional information to a type (for example, if
+/// you were transforming a type `T` to `(T, CtxDerivedFromT)`) then you should
+/// use [`AndMapMutator`], which is more efficient for this usecase.
 pub struct MapMutator<From, To, M, Parse, Map, Cplx>
 where
     From: Clone + 'static,

fuzzcheck/src/mutators/unique.rs

@@ -10,7 +10,8 @@ use crate::Mutator;
 const SIZE_BLOOM: usize = 10_000_000;
 const FALSE_POSITIVE_RATE: f64 = 0.000_001;
 
-/// Experimental mutator which tries to prevent duplicate values to be tested, using a bloom filter
+/// Experimental mutator which tries to prevent a value from being tested more
+/// than once (using a bloom filter).
 ///
 /// **Important:** this mutator cannot be used as a submutator.
 pub struct UniqueMutator<T, TH, Focus, M>