Implement blackbox in Golang (#250)

* Initial release

docs/dev.md

@@ -0,0 +1,36 @@
+Developer Info
+==============
+
+Code submissions are gladly welcomed! The code is fairly easy to read.
+
+Get the code:
+
+```
+git clone git@github.com:StackExchange/blackbox.git
+```
+
+Test your changes:
+
+```
+go test ./...
+```
+
+This runs through a number of system tests. It creates a repo,
+encrypts files, decrypts files, and so on. You can run these tests to
+verify that the changes you made didn't break anything. You can also
+use these tests to verify that the system works with a new operating
+system.
+
+Please submit tests with code changes:
+
+The best way to change BlackBox is via Test Driven Development. First
+add a test to `tools/confidence.sh`. This test should fail, and
+demonstrate the need for the change you are about to make. Then fix
+the bug or add the feature you want. When you are done, `make
+confidence` should pass all tests. The PR you submit should include
+your code as well as the new test. This way the confidence tests
+accumulate as the system grows as we know future changes don't break
+old features.
+
+Note: More info about compatibility are on the [Compatibility Page](compatibility.md)
+