Add config param floating_ip_pool_always_allocate

Fix #61
Update floating_ip_pool_always_allocate description
Merge pull request #92 from ggiamarchi/issue61

Add config param floating_ip_pool_always_allocate
Add attach volume support

issue #24
Get volume support for both api v1 & v2

issue #24
Resolve volumes error handling

issue #24
Resolve volumes tests

issue #24