Signed-off-by: Jessica Yao <jessica@heptio.com>

Document brew install

Signed-off-by: Joe Beda <joe.github@bedafamily.com>

Fix segfault for ks diff

Improve ks init help message

Output usage and return when no command args are provided for `ks diff`.

[docs][prototypes] Rename 'deployment-exposed-with-service' and address README feedback

Improve logging for init

- Add message:  Creating a new app 'foo' at path '/path/to/foo'
- On success, add message:  ksonnet app successfully created! Next, try
  creating a component with `ks generate`
- On failure, provide suggestions for the user.
- Make note that the context is retrieved from the kubeconfig file at
  the environment variable $KUBECONFIG

Specifically,

1. Place more emphasize on project initialization based on context
2. Place ksonnet-lib details into footer.
3. Order examples based on most common use cases.
4. Suggest to visit ks generate

Rename <env>.jsonnet file to main.jsonnet

Fix `nil` dereference error in #129

In line 161 of `root.go`, we're failing to check whether a cluster in
the $KUBECONFIG clusters array exists before using it. This will cause a
`nil` dereference error.

Transition system templates to beta.3

Currently, there are limitations around the file system we are using
that does not easily allow renaming of `us-west/prod` to `us-west`, or
vice versa - `us-west` to `us-west/prod`.

This commit will handle the logic to allow for that by moving the file
contents.

Remove command update

[docs] Very minor README edits

[docs] Fix ksonnet concept overview image + minor doc nits

Update is a deprecated command that was ported over from kubecfg. Since
ksonnet has not had any releases yet, it makes little sense to keep the
command.

[docs] Concepts Reference

First pass at CLI documentation formatting fixes

[docs] Update README

Currently, creating a `dev` environment will create a file
`dev.jsonnet`. Creating a `prod` environment will create a file
`prod.jsonnet`. This is a little more complex and prone to error than it
needs to be, especially when we are renaming environments. It will also
make this file easier to refer to in documentation if we give the file a
static name -- `main.jsonnet`.

Normalize environment server URL

Gracefully handle error when kubeconfig not present

YAML, JSON handling for prototype commands

As part of the environments feature, we want to be able to deploy to a
specific cluster given the environment's URI. We cross-check against
kubecfg for this URI's location. For fail-safe comparison, we probably
want to normalize these URIs.

We decided that this would give the users too many options. We should
limit the documentation to Jsonnet.