Add sample ruby-version file.

Also adds some helpful stuff to gitignore.

This is in the spirit of helping beginners, since I think this project
is meant to be very beginner-friendly.

.gitignore

@@ -1,3 +1,9 @@
+# See http://help.github.com/ignore-files/ for more about ignoring files.
+#
+# If you find yourself ignoring temporary files generated by your text editor
+# or operating system, you probably want to add a global ignore instead:
+#   git config --global core.excludesfile ~/.gitignore_global
+
 Vagrantfile
 *.rbc
 *.sassc
@@ -25,3 +31,9 @@ linecache19-0.5.13.gem
 /bin/
 \#*#
 \.#*
+
+# ignore ruby version management stuff
+.rvmrc
+.ruby-version
+.ruby-gemset
+.rbenv

.ruby-version.sample

@@ -0,0 +1 @@
+1.9.3-p448