*: replaced godep with glide

Godep was continually being a drain on development resources of acbuild,
and thus this commit replaces godep with glide. Glide takes advantage of
the golang vendor experiment, and thus this change will drop support for
versions of Go less than 1.5.

The biggest impact this change has is that dependencies are no longer
vendored with acbuild, and are instead fetched at compile time by the
build script. This is done by checking if the `vendor` directory exists,
and running `glide install` if it is not.

.gitignore

@@ -30,3 +30,4 @@ acbuild/acbuild
 # Used in building acbuild
 gopath/
 bin/
+vendor/

.travis.yml

@@ -1,13 +1,17 @@
 language: go
 matrix:
   include:
-    - go: 1.4.2
-    - go: 1.5.1
+    - go: 1.5
+    - go: 1.6
 
 script:
+ - go get github.com/Masterminds/glide
+ - export PATH=$PATH:$GOPATH/bin
  - ./build
  - ./test
 
+install: 
+
 notifications:
   email: false
 

Documentation/hacking.md

@@ -0,0 +1,13 @@
+# Hacking on acbuild
+
+## Dependencies
+
+acbuild uses glide to control the versions of its dependencies. General
+documentation for glide can be found in [the project's
+README](https://github.com/Masterminds/glide/blob/master/README.md).
+
+Here you'll find whatever weird quirks we've found that developers of acbuild
+should be aware of.
+
+- The version of `appc/spec` specified in the `glide.yaml` file needs to match
+  whatever version is vendored by rkt, or the build will fail.