Test packages separately

When running go test against more than one package using
a wildcard operator, the output of the test command will
be withheld until the end of the test run.

Travis is currently hanging consistently on some builds
of go-discoverd and using a wildcard operator in go test
results in a dearth of debugging info. This splits the
travis tests into one per package to make debugging easier.

Signed-off-by: Anthony Bishopric <git@anthonybishopric.com>