Adds america.edu to blacklist

I recently ported this Gem to PHP and got some feedback from the sub-reddit community that included this issue.  I added a failing test (originally to `it "recognizes academic email addresses and domains" do`) and started debugging.  I traced it down to returning true at:

```ruby
def is_academic?(text)
...
    elsif BLACKLIST.any? { |d| domain.name =~ /(\A|\.)#{Regexp.escape(d)}\z/ }
      false
    elsif ACADEMIC_TLDS.include?(domain.tld)
      # Value of domain.tld for "america.edu" is "edu", a valid TLD.  Return true!
      true
    elsif match_academic_domain?(domain)
      true
...
```

At this point, I moved the test from "recognizes...domains" to the blacklist case and updated the package blacklist to include `america.edu`.

More feedback from PHP-land at:
http://www.reddit.com/r/PHP/comments/2assv5/identify_email_addresses_or_domains_names_that/