bump dependencies to eliminate vulnerabilities (#236)

* bump dependencies to eliminate vulnerabilities
kube 0.71->0.82
k8s-openapi 0.14->0.18
remove failure
env_logger 0.7.1->0.10
tokio-test 0.2.0-alpha.6->-0.4
reqwest 0.10.2->0.11
replace failure::_core::time::Duration with std::time::Duration

* replace chrono::Date with chrono::DateTime
remove redundant imports
downgrade kube 0.82->0.71
downgrade k8s-openapi 0.18->0.14