Update docs

Author: OlivierHnt

docs/src/manual/construction.md

@@ -145,13 +145,12 @@ interval(1) # considered "guaranteed" as the user explicitly constructed the int
 
 In contrast, a [`BareInterval`](@ref) can only be constructed via [`bareinterval`](@ref), it is not a subtype of `Real`, and there are no allowed conversion with `Number`. Thus, this interval type is always guaranteed.
 
-
 !!! danger
-    A user interested in validated numerics should **always** have a resulting interval for which [`isguaranteed`](@ref) is `true`.
+    A user interested in validated numerics should **always** track down the source of an "NG" label.
 
 
 
-## More constructors
+### More constructors
 
 The submodule `IntervalArithmetic.Symbols` exports the infix operator `..` and `±` as an alias for `interval`; this submodule must be explicitly imported.
 

docs/src/manual/usage.md

@@ -123,9 +123,10 @@ One can refer to the following:
 - `setdiff`: cannot be used with intervals. See instead [`interiordiff`](@ref).
 
 
+
 ## Piecewise functions
 
-Since intervals don't play well with `if .. else .. end` statement,
+Since intervals don't play well with `if ... else ... end` statement,
 we provide a utility to define function by pieces:
 
 ```@repl usage
@@ -141,6 +142,7 @@ The resulting function work with both standard numbers and intervals,
 and deal properly with the decorations of intervals.
 
 
+
 ## Custom interval bounds type
 
 A `BareInterval{T}` or `Interval{T}` have the restriction `T <: Union{Rational,AbstractFloat}` which is the parametric type for the bounds of the interval. Supposing one wishes to use their own numeric type `MyNumType <: Union{Rational,AbstractFloat}`, they must provide their own arithmetic operations (with correct rounding!).