Refactor OrphanImporter#extract_orphans

+ Remove unnecessary return
+ alter control flow - don't check for duplicates if no spreadsheet 
+ remove unused variable assignment
Swap return responsibilities in OrphanImporter

Returning false seems like the concern of the exception logging method, not of the add import errors method.
OrphanImporter#import_orphan refactor

+ Use #inject 
+ Use existing add_import_errors method where possible
+ Remove unnecessary variable assignment
+ Improve the check_for_duplicates loop
OrphanImporter - prefer string interp
OrphanImporter - concat strings with <<, not +=

This can be up to 25% faster, as += creates intermediary strings.
Fix typo in OrphanImporter spec
OrphanImporter: decrease public API size
index view
remove inherited controller
double negative spec
OSRA-313 Re-enable RSpec config

https://osraav.atlassian.net/browse/OSRA-313

 - uncomment config settings in spec/spec_helper.rb
 - fix failures in orphan_spec that resulted from enabling
   `mocks.verify_partial_doubles = true` (L77)

OSRA-313 #Code-Review
Merge pull request #245 from NikitaAvvakumov/osra-313-reenable-rspec-config

OSRA-313 Re-enable RSpec config
OSRA-313 #Resolve
Merge pull request #232 from nateberkopec/refactor-importer

Refactor OrphanImporter
test for authentication
Merge pull request #242 from theB264/osra289_create_partners_index

OSRA-289 #Done