Improvements

• Connecting to Saasu using the new API
• New Lightning look and feel
• Renamed labels:
  • Contact
    • Saasu Contact UID -> External ID
    • Saasu Sync Error -> Sync Error
    • Sync to Saasu -> Sync Contact
  • Opportunity
    • Saasu Sales UID -> External ID
    • Saasu Invoice Number -> Invoice Number
    • Saasu Sale Type -> Sale Type
    • Saasu Sync Error -> Sync Error
    • Sync to Saasu -> Sync Opportunity