Fix has_setler call example.

After reading the code, it seems to me has_setler requires a single argument (the table).
Merge pull request #27 from ebouchut/patch-1

Fix has_setler call example.
Adds .travis.yml
Adds Travis badge to README
remove cover_me and get the test running with minutest (two fails)

  1) Failure:
SettingsTest#test_implementations_are_independent [/Users/rachel/work/setler/test/settings_test.rb:167]:
Expected {"foo"=>:test} to not be equal to {"foo"=>:test}.


  2) Failure:
SettingsTest#test_all_settings [/Users/rachel/work/setler/test/settings_test.rb:90]:
--- expected
+++ actual
@@ -1 +1 @@
-{"test2"=>"bar", "test"=>"foo"}
+{"foo"=>:test, "test"=>"foo", "test2"=>"bar"}
remove test pollution from setting default in earlier test
defaults are not shared between different settings classes
add a note in the README about the attr_protected gem for rails 3 -> rails 4 upgraders
rename method in scoped_settings and add a comment about why we can't use activesupport default constantice