Update licensing

Docstrings don't have to be enclosed in triple quotes; update GPL
exception to apply to all strings to reduce confusion and licensing
issues.

LICENSE

 pyrcb is licensed under the GNU Lesser General Public License as
 published by the Free Software Foundation, either version 3 of the
-License or (at your option) any later version. See "licenses/LGPL-3.0"
+License, or (at your option) any later version. See "licenses/LGPL-3.0"
 or <http://www.gnu.org/licenses/> for a copy of the license.
 As an additional permission under GNU GPL version 3 section 7, you may
 distribute non-source forms of comments (lines beginning with "#") and
-docstrings (text enclosed in triple quotation marks) in pyrcb source
-code without the copy of the GNU GPL normally required by section 4,
-provided you include a URL through which recipients can obtain a copy
-of the Corresponding Source and the GPL at no charge.
+strings (text enclosed in quotation marks) in pyrcb source code without
+the copy of the GNU GPL normally required by section 4, provided you
+include a URL through which recipients can obtain a copy of the
+Corresponding Source and the GPL at no charge.
 Files under "examples/" have been released to the public domain. See
-"licenses/CC0-1.0" for a copy of the CC0 Public Domain Dedication.
+"licenses/CC0-1.0" or <http://creativecommons.org/publicdomain/zero/1.0/>
+for a copy of the CC0 Public Domain Dedication.
 Files under "docs/" are part of pyrcb-docs, documentation for pyrcb.
 pyrcb-docs is licensed under the GNU Lesser General Public License

pyrcb.py

@@ -8,10 +8,10 @@
 #
 # As an additional permission under GNU GPL version 3 section 7, you may
 # distribute non-source forms of comments (lines beginning with "#") and
-# docstrings (text enclosed in triple quotation marks) in pyrcb source
-# code without the copy of the GNU GPL normally required by section 4,
-# provided you include a URL through which recipients can obtain a copy
-# of the Corresponding Source and the GPL at no charge.
+# strings (text enclosed in quotation marks) in pyrcb source code without
+# the copy of the GNU GPL normally required by section 4, provided you
+# include a URL through which recipients can obtain a copy of the
+# Corresponding Source and the GPL at no charge.
 #
 # This program is distributed in the hope that it will be useful,
 # but WITHOUT ANY WARRANTY; without even the implied warranty of