Use new prompt detection in run_command to detect aptitude prompts

Also adds flags to aptitude command when force=yes is used, in order
to bypass the prompts given for untrusted packages.

Fixes #31
Add mention of fetch module to the copy module docs.
Merge pull request #301 from geerlingguy/add-fetch-mention

Add mention of fetch module to the copy module docs.
Fix EC2_EIP: don't try to associate an already-associated instance.
EC2_EIP: add status='allocated' to allocate new elastic IP addresses
EC2_EIP: fix reusing un-associated elastic IPs