0.4.1

A few minor fixes.

• Fixed some uses of Nullable to get rid of deprecation messages related to its alias this being deprecated. However, there is one that I've seen pop up when projects use dxml (it also pops up with dxml's unit tests) which I have not been able to track down. Namely:

  /usr/local/include/dmd/std/range/primitives.d(174,38): Deprecation: function std.typecons.Nullable!string.Nullable.get_ is deprecated - Implicit conversion with alias Nullable.get this will be removed after 2.096. Please use .get explicitly.

  It looks like somewhere, a range of Nullables is being tested to see whether it's an input range or not, and that test results in the deprecation message being printed, but I have no clue where the code is that's using isInputRange and thus triggers the deprecation message.

  Using a version of Phobos where Nullable'salias this has been completely removed instead of deprecated results in dxml's tests building and passing just fine. So, it seems that whatever is going on doesn't actually require that any code be changed because of the deprecation, much as it's annoying to have the deprecation message being printed.

• Fixed #14: The missing message was added to the assertion in DOMEntity.children.

• Fixed #19: dxml.util.stripIndent was fixed to properly handle the case where the second line was just whitespace, and the first line did not start with whitespace.