kubecfg: improve tests around authentication

This change adds additional test coverage for the kubecfg
command. There is now a test for the case when the auth info
file does not exist. LoadAuthInfo tests have been refactored
to use table testing.
Add a sanity check for running etcd servers to the integration test script.
Use http.StatusInternalServerError instead of 500
Allow API_PORT to be changed via hack/local-up
Fix typo in README
Remove extra test flags from all commands

Currently all commands are being build with extra flags. The extra
flags appear because of a direct import of the testing package from
the fake_etcd_client.go source file.

Remove the direct import of the testing package. Add a tools.T
interface to support existing behavior. Also clean up two TODO items
by remove using of the expectError and expectNoError functions.

Fixes #579
Add go fuzzer in preparation for testing. Also gofmt a few files that needed it.
Merge pull request #652 from kelseyhightower/fix_readme_typo

Fix typo in README
Merge pull request #650 from smarterclayton/use_constant_code

Use http.StatusInternalServerError instead of 500
Merge pull request #645 from brendandburns/integration

Add a sanity check for existing etcd servers to the integration test script
Use 'go install' to build all commands at the same time.

'go build' compiles the packages but discards the results if multiple packages specified.
Add TODOs, clean up, clarify comments, and add one more test.
Fixing typos
Merge pull request #658 from danmcp/fix_typos

Fixing typos
Fixing Typos
Merge pull request #660 from danmcp/fix_typos

Fixing Typos

Thanks for the fix.
Merge pull request #647 from kelseyhightower/fix_extra_test_flags

Remove extra test flags from all commands
Merge pull request #636 from kelseyhightower/load_auth_info_tests

kubecfg: improve tests around authentication
Merge pull request #630 from lavalamp/fuzz

Add go fuzzer in preparation for testing.
Merge pull request #651 from smarterclayton/allow_api_port_to_change

Allow API_{PORT,HOST} to be changed via hack/local-up