Add libarchive which is required by berkshelf specs.

This libarchive now the only failing test is a berks example: 

http://manhattan.ci.opscode.us/job/chefdk-test/30/
```
[31m(::) failed steps (::)[0m

[31mexpected "Fetching 'berkshelf-cookbook-fixture' from git@github.com:RiotGames/berkshelf-cookbook-fixture.git (at v0.2.0)\nAn error occurred during Git execution:\n\n  Host key verification failed.\n  fatal: Could not read from remote repository.\n  \n  Please make sure you have the correct access rights\n  and the repository exists.\n\n" to include "Permission denied (publickey)."[0m
[31mDiff:[0m
[31m@@ -1,2 +1,9 @@[0m
[31m-Permission denied (publickey).[0m
[31m+Fetching 'berkshelf-cookbook-fixture' from git@github.com:RiotGames/berkshelf-cookbook-fixture.git (at v0.2.0)[0m
[31m+An error occurred during Git execution:[0m
[31m+[0m
[31m+  Host key verification failed.[0m
[31m+  fatal: Could not read from remote repository.[0m
[31m+  [0m
[31m+  Please make sure you have the correct access rights[0m
[31m+  and the repository exists.[0m
[31m (RSpec::Expectations::ExpectationNotMetError)[0m
[31mfeatures/commands/install.feature:351:in `Then the output should contain:'[0m

[31mFailing Scenarios:[0m
[31mcucumber features/commands/install.feature:345[0m[90m # Scenario: installing a Berksfile that contains a Github location and protocol ssh[0m

164 scenarios ([31m1 failed[0m, [32m163 passed[0m)
965 steps ([31m1 failed[0m, [32m964 passed[0m)
1m20.997s
```