Update tocanonical docstring, and remove canonicaldomain (#580)

Author: jishnub

src/Domain.jl

@@ -103,18 +103,18 @@ issubcomponent(a::Domain,b::Domain) = a in components(b)
 
 ##### canoncial
 """
-    canonicaldomain(d)
-
-returns a domain which we map to for operations. For example,
-the canonical domain for an interval [a,b] is [-1,1]
-"""
-function canonicaldomain end
+    tocanonical(d, x)
 
+Map the point `x` in `d` to a point in `DomainSets.canonicaldomain(d)`.
 
-"""
-    tocanonical(d, x)
+# Examples
+```jldoctest
+julia> tocanonical(0..0.5, 0)
+-1.0
 
-maps the point `x` in `d` to a point in `canonical(d,x)`
+julia> tocanonical(0..0.5, 0.5)
+1.0
+```
 """
 function tocanonical end