add proper credits to copyright holders

Author: eksperimental

LEGAL

@@ -1,8 +1,9 @@
 LEGAL NOTICE INFORMATION
 ------------------------
 
-All the files in this distribution are covered under either Elixir's
-license (see the file LICENSE) except the files mentioned below that
-contains sections that are under Erlang's License (EPL):
+All the files in this distribution are copyright (c) 2012 Plataformatec
+covered under Elixir's license (see the file LICENSE) except the file
+mentioned below that contains sections that are copyright
+(c) 1996 Ericsson AB under Erlang's License (EPL):
 
 lib/elixir/src/elixir_parser.erl (generated by build scripts)