* Uniform treatment of Leanpub books

free Leanpub books come in two flavors
- free to read online without an account or email address
- free to read after a "purchase" with a minimum price of "Free!" A
valid email is requested to create an account, but you can read   or
download even if the email is bogus.

After some consideration, I'm proposing that the free-to-read books
should be without any annotation, and the free-after-"purchase" books
be denoted as *(Leanpub Account or valid email requested)* . This PR
implements that for the english lists.

Comments requested!

* add required space