Allow -k option to bypass ssl errors (like curl)

[subt13]

$ openapi2apigee generateApi petStore -s http://petstore.swagger.io/v2/swagger.json -D -d /Users/me/Desktop/ { stack: 'ResolverError: Error downloading https://petstore.swagger.io:443/v2/swagger.json \n' + 'unable to get local issuer certificate\n' + ' at C:\Users\\AppData\Roaming\npm\node_modules\openapi2apigee\node_modules\@apidevtools\json-schema-ref-parser\lib\resolvers\http.js:127:16\n' + ' at processTicksAndRejections (internal/process/task_queues.js:93:5)', code: 'ERESOLVER', message: 'Error downloading https://petstore.swagger.io:443/v2/swagger.json \n' + 'unable to get local issuer certificate', source: 'https://petstore.swagger.io:443/v2/swagger.json', path: null, toJSON: [Function: toJSON], ioErrorCode: 'UNABLE_TO_GET_ISSUER_CERT_LOCALLY', name: 'ResolverError', footprint: 'null+https://petstore.swagger.io:443/v2/swagger.json+ERESOLVER+Error downloading https://petstore.swagger.io:443/v2/swagger.json \n' + 'unable to get local issuer certificate', toString: [Function: toString]