[trivial] typo 'isPriavte' should be 'isPrivate'.

All relevant tests based as expected.

% hub --version
git version 1.9.3 (Apple Git-50)
hub version 1.12.2-gb311b7b

./script/test
Failing Scenarios:
cucumber -p all features/bash_completion.feature:8 # Scenario: "pu" matches multiple commands including "pull-request"
cucumber -p all features/bash_completion.feature:14 # Scenario: "ci-" expands to "ci-status"
cucumber -p all features/bash_completion.feature:18 # Scenario: Offers pull-request flags
cucumber -p all features/bash_completion.feature:23 # Scenario: Doesn't offer already used pull-request flags
cucumber -p all features/bash_completion.feature:28 # Scenario: Browse to issues
cucumber -p all features/bash_completion.feature:32 # Scenario: Browse to punch-card graph
cucumber -p all features/bash_completion.feature:36 # Scenario: Completion of fork argument

245 scenarios (7 failed, 238 passed)
1448 steps (7 failed, 1441 passed)
1m54.153s