Prepend --script to disable all parted prompts.

Fixes #39
Merge pull request #42 from jrafanie/disable_parted_prompts

Prepend --script to disable all parted prompts.
Strip leading whitespace of each line from pvdisplay and friends.
Merge pull request #45 from jrafanie/strip_leading_whitespace_when_parsing_pvdisplay_and_friends

Strip leading whitespace of each line from pvdisplay and friends.
Raise specific NoSuchFileError for missing files

Strip params to avoid clear text passwords
Update spec to expect the appropriate error