Added a contributor list and some contributor instructions.

.gemspec

@@ -15,11 +15,11 @@ GEMSPEC = Gem::Specification.new do |gem|
   EOF
   gem.rubyforge_project  = 'openpgp'
 
-  gem.authors            = ['Arto Bendiken', 'Kévin Lacointe']
+  gem.authors            = ['Arto Bendiken']
   gem.email              = 'arto.bendiken@gmail.com'
 
   gem.platform           = Gem::Platform::RUBY
-  gem.files              = %w(AUTHORS README UNLICENSE VERSION bin/openpgp) + Dir.glob('lib/**/*.rb')
+  gem.files              = %w(AUTHORS CONTRIBUTORS README UNLICENSE VERSION bin/openpgp) + Dir.glob('lib/**/*.rb')
   gem.bindir             = %q(bin)
   gem.executables        = %w(openpgp)
   gem.default_executable = gem.executables.first

AUTHORS

@@ -1,2 +1 @@
-* Arto Bendiken <arto.bendiken@gmail.com> (Lead developer)
-* Kévin Lacointe <kevinlacointe@gmail.com> (Some GnuPG patches)
+* Arto Bendiken <arto.bendiken@gmail.com>

CONTRIBUTORS

@@ -0,0 +1 @@
+* Kévin Lacointe <kevinlacointe@gmail.com> (Some GnuPG patches)

README.md

@@ -97,10 +97,35 @@ Authors
 -------
 
 * [Arto Bendiken](mailto:arto.bendiken@gmail.com) - <http://ar.to/>
-* [Kévin Lacointe](mailto:kevinlacointe@gmail.com)
+
+Contributors
+------------
+
+* [Kévin Lacointe](mailto:kevinlacointe@gmail.com) - <http://github.com/klacointe>
+
+Contributing
+------------
+
+* Do your best to adhere to the existing coding conventions and idioms.
+* Don't use hard tabs, and don't leave trailing whitespace on any line.
+* Do document every method you add using [YARD][] annotations. Read the
+  [tutorial][YARD-GS] or just look at the existing code for examples.
+* Don't touch the `.gemspec` or `VERSION` files. If you need to change them,
+  do so on your private branch only.
+* Do feel free to add yourself to the `CONTRIBUTORS` file and the
+  corresponding list in the the `README`. Alphabetical order applies.
+* Don't touch the `AUTHORS` file. If your contributions are significant
+  enough, be assured we will eventually add you in there.
+* Do note that in order for us to merge any non-trivial changes (as a rule
+  of thumb, additions larger than about 15 lines of code), we need an
+  explicit [public domain dedication][PDD] on record from you.
 
 License
 -------
 
 OpenPGP.rb is free and unencumbered public domain software. For more
 information, see <http://unlicense.org/> or the accompanying UNLICENSE file.
+
+[YARD]:      http://yardoc.org/
+[YARD-GS]:   http://yardoc.org/docs/yard/file:docs/GettingStarted.md
+[PDD]:       http://lists.w3.org/Archives/Public/public-rdf-ruby/2010May/0013.html