typo fix in docs and advocate for wrapper struct if custom serializat…

…ion is used (#407)

* typo fix in docs

* add warning about already defined custom serialization

* add warning about already defined custom serialization

* add warning about already defined custom serialization

docs/src/customserialization.md

@@ -23,6 +23,11 @@ Base.convert(::Type{ASerialization}, a::A) = ASerialization([a.x])
 Base.convert(::Type{A}, a::ASerialization) = A(only(a.x))
 ```
 
+!!! warning "Already defined custom serialization"
+    Take care, some Julia internal types already use a `CustomSerialization` and JLD2.jl cannot nest them.
+    In order to avoid unexpected behavior you should define a wrapper type,
+    such as in the example above `ASerialization` even if you could use a simple Julia built in type (as in this case `Vector{Int}`).
+
 If you do not want to overload `Base.convert` then you can also define
 
 ```julia
@@ -47,4 +52,4 @@ arr = [B(rand()) for i=1:10]
 ```
 
 In this example JLD2 converts the array of `B` structs to a plain `Vector{Float64}` prior to 
-storing to disk.
+storing to disk.

docs/src/hdf5compat.md

@@ -131,4 +131,4 @@ it is shown here as it serves as a good example for usage of that feature.
 ```
 
 Usually one would also have to define a method for `wconvert`. However, in this 
-case JLD2 figures out that ne explicit conversion is needed to construct `nothing`.
+case JLD2 figures out that no explicit conversion is needed to construct `nothing`.