adding handling so that missing callouts will not break entire build
Merge pull request #48 from oreillymedia/sarah

Adding handling so that missing callouts will not break entire build
adding .editorconfig
fixing code-style: indentation, final newlines and trailing whitespaces
fixing lint warn: don't use deprecated method `File.exists?`
fixing lint warn: shadowing outer local variable
fixing lint warn: unused block argument
fixing code-style: avoid using {...} for multi-line blocks
fixing code-style: redundant return
fixing code-style: use fail instead of raise to signal exceptions
fixing code-style: better align array in constants.rb
fixing code-style: remove redundant empty lines and add space after comma
fixing code-style: use next to skip iteration
fixing code-style: use the new Ruby 1.9 hash syntax
fixing code-style: be more consistent with single/double quotes