better messages, fix typos

- transition-step-1 (`transition_url` variable needed): we indicate that there

is a new version of the lesson that is available for testing, and that it will be deprecated in the future.

- transition-step-2 (`transition_url` and `transition_date` variables needed): we indicate that a new version of the lesson is avaiable with a deprecation date.

- transition-step-3 (`transition_url` variable needed): the lesson if fully deprecated, and a redirect is set up to the new URL

- transition-step-3 (`transition_url` variable needed): the lesson is fully deprecated, and a redirect is set up to the new URL

{% endcomment %}

{% elsif site.life_cycle == "transition-step-1" %}

{% include check_transition_variables.html need_transition_date = 'false' %}

<div class="alert alert-warning life-cycle">

  A newer version of this lesson is being tested:

  A newer version of this lesson is being tested on The Carpentries Workbench:

  <a href="{{ site.transition_url }}">{{ site.transition_url }}</a>.

  This lesson will become deprecated in the near future.

  The Jekyll version of this lesson will become deprecated in the near future.

</div>

{% elsif site.life_cycle == "transition-step-2" %}

{% include check_transition_variables.html need_transition_date = 'true' %}

<div class="alert alert-danger life-cycle">

  A newer version of this lesson is available from: <a href="{{ site.transition_url }}">{{ site.transition_url }}</a>.

  This lesson will become deprecated on {{ site.transition_date }}.

  A newer version of this lesson is available from:

  <a href="{{ site.transition_url }}">{{ site.transition_url }}</a>.

  The Jekyll version of this lesson will become deprecated on

  {{ site.transition_date }}.

</div>

{% elsif site.life_cycle == "transition-step-3" %}

{% include check_transition_variables.html need_transition_date = 'false' %}

<div class="alert alert-danger life-cycle">

    This lesson is deprecated. A newer version is available from: <a href="{{ site.transition_url }}">{{ site.transition_url }}</a>.

  You are veiwing a deprecated version of this lesson. An updated version is

  available from:

  <a href="{{ site.transition_url }}">{{ site.transition_url }}</a>.

</div>

{% endif %}