Add basic tests

[lachenmayer]

I added some new tests in #5 and I just wanted to double check that I didn't mess up the test implementation.

This just adds the example script as a basic test.

Some of the existing tests are failing, even with random-access-file:

# read empty
not ok 4 no error
  ---
    operator: error
    expected: |-
      undefined
    actual: |-
      { [Error: ENOENT: no such file or directory, open '/var/folders/z8/xq1r3qcd7szbpx1_77xsgpqc0000gn/T/random-access-file-58676-1531846996824/create-empty.txt'] errno: -2, code: 'ENOENT', syscall: 'open', path: '/var/folders/z8/xq1r3qcd7szbpx1_77xsgpqc0000gn/T/random-access-file-58676-1531846996824/create-empty.txt' }
    at: Request._callback (/Users/harry/Documents/node_modules/random-access-test/index.js:23:11)
    stack: |-
      Error: ENOENT: no such file or directory, open '/var/folders/z8/xq1r3qcd7szbpx1_77xsgpqc0000gn/T/random-access-file-58676-1531846996824/create-empty.txt'
  ...
not ok 5 empty buffer
  ---
    operator: deepEqual
    expected: <Buffer >
    actual:   undefined
    at: Request._callback (/Users/harry/Documents/node_modules/random-access-test/index.js:24:11)
    stack: |-
      Error: empty buffer
          at Test.assert [as _assert] (/Users/harry/Documents/node_modules/random-access-test/node_modules/tape/lib/test.js:224:54)
          at Test.bound [as _assert] (/Users/harry/Documents/node_modules/random-access-test/node_modules/tape/lib/test.js:76:32)
          at Test.tapeDeepEqual (/Users/harry/Documents/node_modules/random-access-test/node_modules/tape/lib/test.js:421:10)
          at Test.bound [as same] (/Users/harry/Documents/node_modules/random-access-test/node_modules/tape/lib/test.js:76:32)
          at Request._callback (/Users/harry/Documents/node_modules/random-access-test/index.js:24:11)
          at Request.callback (/Users/harry/Documents/node_modules/random-access-test/node_modules/random-access-storage/index.js:161:8)
          at nextTickCallback (/Users/harry/Documents/node_modules/random-access-test/node_modules/random-access-storage/index.js:249:7)
          at process._tickCallback (internal/process/next_tick.js:63:19)
  ...

# bad truncate
not ok 24 should be truthy
  ---
    operator: ok
    expected: true
    actual:   null
    at: Request._callback (/Users/harry/Documents/node_modules/random-access-test/index.js:133:15)
    stack: |-
      Error: should be truthy
          at Test.assert [as _assert] (/Users/harry/Documents/node_modules/random-access-test/node_modules/tape/lib/test.js:224:54)
          at Test.bound [as _assert] (/Users/harry/Documents/node_modules/random-access-test/node_modules/tape/lib/test.js:76:32)
          at Test.assert (/Users/harry/Documents/node_modules/random-access-test/node_modules/tape/lib/test.js:342:10)
          at Test.bound [as ok] (/Users/harry/Documents/node_modules/random-access-test/node_modules/tape/lib/test.js:76:32)
          at Request._callback (/Users/harry/Documents/node_modules/random-access-test/index.js:133:15)
          at Request.callback (/Users/harry/Documents/node_modules/random-access-test/node_modules/random-access-storage/index.js:161:8)
          at ontruncate (/Users/harry/Documents/node_modules/random-access-test/node_modules/random-access-file/index.js:163:9)
          at FSReqWrap.oncomplete (fs.js:145:20)
  ...

Not sure what the correct behavior is meant to be.

[kenOfYugen]

I came across the same issue, while making a new provider.
For example, the read empty test passes with random-access-file, by adding the {writable: true} option as implemented in the internal tests.
So in this case, should the conformance test, or the random-access-file implementation be changed? Basically the question I ask is, can the spec be considered stable?