Begin work on a generic "attribute" command to reduce duplication
Completely strip Ppl::Command::Phone of duplicate functionality now supported by
Ppl::Command::Attribute
Implement Ppl::Command::Attribute#add_attribute and deduplicate `ppl email`
Remove dead code from Ppl::Command::Phone
Implement Ppl::Command::Attribute#remove_attribute

This adds the ability to remove a given value from a contact's attribute list
Deduplicate Ppl::Command::Url
Deduplicate Ppl::Command::Org and simultaneously add support for multiple
organizations per contact instead of just one
Make Ppl::Commmand::Attribute#remove_attribute actually delete the value
Upgrade phone number support so that multiple numbers per contact are allowed
Version bump for 1.10.0
Merge branch 'dedup' into 1.10.0