deflake tests.
Merge pull request #887 from brendandburns/proxy

Deflake proxy unit tests.
Add a tear down option to the e2e, that just tears down the cluster
Useful for cleaning state after failed runs.
Merge pull request #892 from brendandburns/teardown

Add a teardown option to the e2e, that just tears down the cluster, also make gce teardown synchronous.
Allow kubecfg to parse other types via register function
Use register function for default types as well
Change package level variable to instance variable of new parser type
Use interface{} instead of reflect.Type for storage type map
Convert map in NewParser