Fix bug in parsing TEL content. Rework unit tests.

- newVC3_Tel was not assigning the value provided to the constructed
  object.
- Private unit tests were run every time the code was compiled due to
  how the unittest library works. These now only run as part of the unit
  tests with `nimble test`.

vcard.nimble

@@ -1,6 +1,6 @@
 # Package
 
-version       = "0.1.2"
+version       = "0.1.3"
 author        = "Jonathan Bernard"
 description   = "Nim parser for the vCard format version 3.0 (4.0 planned)."
 license       = "MIT"