Aspell mods and a few grammar fixes

Ran aspell on each *.md file.  I was attempting to be liberal about the changes and ignore Aspell wanting to change words like "metaprogramming" to "meta-progamming" and "refactoring" to "re-factoring" because whether Aspell is correct or not, it didn't seem like a big enough change.


I think "seedable" is more appropriate here, despite it being colloquial.