chore(client): remove unused client tests

We use integration tests to check the expected output of certain
commands. These tests have been unused and unmodified in quite some
time. Maybe when we rewrite the client in Go, we can draw upon these
for inspiration, but right now they aren't doing much.
Merge pull request #1526 from deis/remove-client-tests

chore(client): remove unused client tests
ref(tests): move test commands into code

Deis' integration tests are more approachable without the
indirection of looking them up from a JSON fixture.
ref(tests): move exported Test* funcs to top of files and tidy up code
ref(tests): combine and shorten names of Go utility packages
fix(tests): remove GetCommand() func and vendored simplejson package