Introduce backend prefix annotation.

To support backends that host endpoints different than the ones exposed in an ingress resource, we are introducing backend prefix annotations. This allows the ingress controller to setup a backend prefix HTTP setting for endpoints mentioned in an ingress resource with this annotation.

Read more about the usage of the backend prefix annotation here:
https://azure.github.io/application-gateway-kubernetes-ingress/docs/annotations.html#backend-path-prefix

Issues fixed:
#49

Introduce Backed prefix annotation

To support backends that host endpoints different than the ones exposed in an ingress resource, we are introducing backend prefix annotations. This allows the ingress controller to setup a backend prefix HTTP setting for endpoints mentioned in an ingress resource with this annotation.

Read more about the usage of the backend prefix annotation here:
https://azure.github.io/application-gateway-kubernetes-ingress/docs/annotations.html#backend-path-prefix

Fixes ingress controller behavior during service deletion

Release Notes:
#59 : The ingress controller no longer errors out when a service referenced in the Ingress resource is not present. Paths for which services have not yet been launched in k8s the ingress controller will still install the paths in the application gateway, but with empty backend pools.

Fixes ingress controller behavior during service deletion

Also fixes travis-ci deployment.

Fixes ingress controller issues with service deletion

Also, we want to test our docker container image push in the candidate release.

0.1.3: Fix for service delete issue

• Fix in backend pool and backend http settings to address service deletion. #58