Configuration module

Based on
http://gregmoreno.wordpress.com/2012/06/07/how-to-create-a-wrapper-gem-f
or-service-apis-part-1/
Add rspec as development dependency
Commit Gemfile.lock

The guide recommended putting Gemfile.lock into source control
Initial tests for configuration
Add faraday gem as dependency
Initial transaction class
Docs for transaction initialize
Initial Client WIP
Use array for keys
Update Gemfile.lock
Specs for api_key and endpoint setting via block
Rename variable
Update describes in transaction spec
First spec for transaction
Check that hash is given
Test transaction block configuration
Spec for mixing up config
Spec for prioritizing block values
Refactor parsing through keys
Check for nil or empty param values