Avoid relying on global state so spec can be run focused

Signed-off-by: Abhijit Hiremagalur <abhi@pivotallabs.com>
Better name for local variable

Signed-off-by: Abhijit Hiremagalur <abhi@pivotallabs.com>
Backfill spec for precarious Client <=> AgentClient interaction

Signed-off-by: Abhijit Hiremagalur <abhi@pivotallabs.com>
Avoid dynamic method creation and relying on inheritance

Signed-off-by: Abhijit Hiremagalur <abhi@pivotallabs.com>
Convert AgentClient initialize to `with_defaults`

Signed-off-by: Abhijit Hiremagalur <abhi@pivotallabs.com>
Move Director::Client functionality into Director::AgentClient

  * removes convoluted interdependency between two classes

Signed-off-by: Abhijit Hiremagalur <abhi@pivotallabs.com>
Update README.md

Added in instructions to build stemcell from the latest bosh version.