replace instance variables with let syntax
in card a checklist specs. Fixes incompatability
between ruby-2.0 and activemodel dependency which
call #initialize_dup as a public method
Merge pull request #41 from rossta/ruby_head_compatability

Make specs compatible with ruby-head
use Client as an instance rather than a class
add configuration class
for configuration auth policy and credentials
client now access auth policy instance rather than class for api requests
configurable client via Trello.configure convention
oauth token secret not required
rename trello oauth token secret
make 3-legged oauth available via configuration
documentation for configure dsl
README update
namespace Configuration tests to prevent rspec conflicts for ruby 1.9.2
Merge pull request #42 from rossta/configurable_client

Configurable client