docs(applications) fix broken links for SSH keys

Links were broken because they included the Markdown file extension.

Author: lenn4rd

src/applications/using-buildpacks.md

@@ -3,10 +3,10 @@
 Deis supports deploying applications via [Heroku Buildpacks][]. Buildpacks are useful if you're interested in following Heroku's best practices for building applications or if you are deploying an application that already runs on Heroku.
 
 ## Add SSH Key
- 
+
 For **Buildpack** based application deploys via `git push`, Deis Workflow identifies users via SSH keys. SSH keys are pushed to the platform and must be unique to each user.
 
-- See [this document](../users/ssh-keys.md/#generate-an-ssh-key) for instructions on how to generate an SSH key.
+- See [this document](../users/ssh-keys/#generate-an-ssh-key) for instructions on how to generate an SSH key.
 
 - Run `deis keys:add` to upload your SSH key to Deis Workflow.
 
@@ -15,7 +15,7 @@ $ deis keys:add ~/.ssh/id_deis.pub
 Uploading id_deis.pub to deis... done
 ```
 
-Read more about adding/removing SSH Keys [here](../users/ssh-keys.md/#adding-and-removing-ssh-keys).
+Read more about adding/removing SSH Keys [here](../users/ssh-keys/#adding-and-removing-ssh-keys).
 
 ## Prepare an Application
 

src/applications/using-dockerfiles.md

@@ -7,7 +7,7 @@ Dockerfiles are incredibly powerful but require some extra work to define your e
 
 For **Dockerfile** based application deploys via `git push`, Deis Workflow identifies users via SSH keys. SSH keys are pushed to the platform and must be unique to each user.
 
-- See [this document](../users/ssh-keys.md/#generate-an-ssh-key) for instructions on how to generate an SSH key.
+- See [this document](../users/ssh-keys/#generate-an-ssh-key) for instructions on how to generate an SSH key.
 
 - Run `deis keys:add` to upload your SSH key to Deis Workflow.
 
@@ -16,7 +16,7 @@ $ deis keys:add ~/.ssh/id_deis.pub
 Uploading id_deis.pub to deis... done
 ```
 
-Read more about adding/removing SSH Keys [here](../users/ssh-keys.md/#adding-and-removing-ssh-keys).
+Read more about adding/removing SSH Keys [here](../users/ssh-keys/#adding-and-removing-ssh-keys).
 
 
 ## Prepare an Application