Reexport subpackages

[ReubenJ]

When using Herb, we usually have to add using HerbGrammar, HerbSearch, etc., meaning we don't get any benefit from using Herb in the first place. This change allows you to access anything exported from HerbGrammar, HerbSearch, etc., after only using Herb.

Before, this failed:

using Herb
# needs using HerbGrammar

# or HerbGrammar.@cfgrammar
g = @cfgrammar begin
    a = 1
end

With this change, it works without the extra using or extra HerbGrammar. before the macro call.

[pwochner]

Nice one, this will make using Herb so much less confusing.