Fix broken links

Thanks to Zoltan Koch for reporting them
Remove the entire "Erlang Websites" question

Mail from Mikael Remond 2014-06-16 says planeterlang is off the
air until further notice.
Update 'commercial Erlang users'

Aptela have been bought out.
Ubiquiti is new.
Both in response to mail from Mahesh Paolini-Subramanya 2014-06-16