add .gitattributes

This improves method detection for Ruby source files;
making output of "git diff" and "git log -p -W" more
readable for git users looking at our Ruby code.

git will automatically notice this file and start using
it when generating diff output.

See the gitattributes(5) manpage for more details.
Ruby pattern definitions reside in userdiff.c of the
git sources at git://git.kernel.org/pub/scm/git/git.git

* .gitattributes: new file for git users
  [ruby-core:71578] [Feature #11713]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@52674 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

.gitattributes

@@ -0,0 +1,5 @@
+*.gemspec diff=ruby
+*.rb diff=ruby
+bin/* diff=ruby
+tool/update-deps diff=ruby
+tool/make-snapshot diff=ruby

ChangeLog

@@ -1,3 +1,8 @@
+Fri Nov 20 06:52:53 2015  Eric Wong  <e@80x24.org>
+
+	* .gitattributes: new file for git users
+	  [ruby-core:71578] [Feature #11713]
+
 Thu Nov 19 22:35:31 2015  Tanaka Akira  <akr@fsij.org>
 
 	* ext/socket/ancdata.c: Check buffer full and ignore MSG_TRUNC flag.