This commit removes any assertion from Go's "testing" package,
preferring instead to use an assertion from the testify package. All
tests now have uniformity.
This also decrease the number of iterations in the password generation
test, decreasing test runtime tenfold
Change-Id: I8799110e93dfa19bebe9050528e865b4c991c3df
This adds the "airshipctl document" tree of commands, as well as one of
its leaf commands, "generate masterpassphrase".
Change-Id: I2365ebe67b38ebbbe4873c6e1beb6407f0e000eb