Kill dead i18n keys

oh this is sweet

---
```
Unused i18n keys (99) | i18n-tasks v0.2.1
update                                       Update
until_close                                  until close
starting                                     Starting
show_more                                    Show More
send_invite                                  Send invite
sending                                      Sending
prev                                         Prev
password                                     Password
other                                        Other
ok_got_it                                    Okay, got it!
next                                         Next
new_activity                                 New activity
id                                           id
group_admin                                  Group Coordinator
participation                                Participation
email_address                                Email address
closing                                      Closing
by                                           by
author                                       Author
about_loomio                                 About Loomio
email.verification.ignore                    If you did not request to join Loomio please ignore this email.
email.verification.intro                     Please click this verification link to finalise your request:
email.verification.header                    You're almost done!
email.proposal_closing_soon.summary          Summary
email.proposal_closing_soon.closes_in        Closes in
email.proposal_closed.intro                  Your proposal "%{proposal_name}" has closed.
email.create_proposal.subject                New proposal: %{which}
email.create_proposal.closes_in              Closes in
email.create_proposal.intro                  A new proposal was created in a Loomio group that you belong to.
group_form.admins_only                       Coordinators only
discussion_form.context                      Context
invitation.invites_more_help2                <p>You can invite people to your group at any time.</p><p>You might want to invite all your members in right away, or you could start by inviting just the people you’re working most closely with.</p>
invitation.subject                           Please join our new Loomio group, %{group}
signing_in                                   Signing in
cancel_my_account                            Cancel my account
password_details                             (we need your current password to confirm your changes)
current_password                             Current password
password_confirmation                        Password confirmation
blank_details                                (leave blank if you don't want to change it)
pricing_page.informal_groups_examples        e.g. families, social movements, collectives
pricing_page.informal_groups_desc            Members of your group will be asked to pay what they can
pricing_page.informal_groups                 Informal groups
pricing_page.organisations_examples          e.g. businesses, government agencies, community organisations
pricing_page.organisations                   Organisations
pricing_page.intro                           Groups with a budget pay a subscription for using the tool.
Groups without the means to pay a subscription use the
Pay What You Can model: their members are invited to make a voluntary contribution.      Your contribution means we can keep Loomio independent, free of advertising, and driven by our community.
position_verbs.past_tense.block              blocked
position_verbs.past_tense.abstain            abstained
position_verbs.past_tense.no                 disagreed
position_verbs.past_tense.yes                agreed
proposal_close_date_error                    Please give a future close date
empty_discussion_list                        There is no activity in this discussion yet.
membership_requested                         Membership requested
confirm_remove_user                          Are you sure you wish to remove %{which_user} from the group?
invited_users                                Invited members
get_in_touch_link                            get in touch
need_more_invites_html                       Need more? Loomio is in closed beta, which means we're still in development and have limited resources for user support. If you'd like to increase the size of your group %{href}.
remaining_invites                            remaining invites
invite_members_to_group                      Invite members to %{which_group}
no_invitations_button                        No invitations left
dashboard_helper_text.message                <p>The home page shows you all of the current discussions in all the groups you are a member of.</p><p>You can start a discussion on a new topic by clicking the “Start a discussion” button.</p>
dashboard_helper_text.header                 Welcome to your Home page
group_helper_text.message                    <p>This is the <strong>group page</strong>. On the left is a list of all the discussions in this group.</p><p>When you want the group to discuss another topic, start a new discussion.</p>
group_helper_text.header                     Welcome to your new group!
discussion_helper_text.message               <p>The topic is at the top of the page, with context underneath.</p><p>Discussion is on the left, decisions come up on the right. If you think the group is ready to make a decision, you can make a proposal for the group to consider.</p>
discussion_helper_text.header                Welcome to your first discussion
generic_confirm                              Are you sure?
or_link_account_html                         Already have a Loomio account? <a href='%{link}'>Link it up</a>
tagline                                      Creating a world where it's easy for anyone to participate in decisions that affect them.
notifications.motion_outcome_updated         updated the outcome for the proposal
inbox.dropdown-btn                           Inbox
success.position_updated                     Position updated.
success.added_to_group                       You have been added to %{which_group}.
warning.user_already_member                  %{which_user} is already a member of this group.
warning.user_already_admin                   %{which_user} is already a coordinator of this group.
warning.position_not_submitted               Your position could not be submitted
warning.membership_request_already_canceled  Membership request has already been canceled.
warning.cant_remove_last_admin               You are the last coordinator and cannot be removed.
notice.invitations.auto_added_and_sent       %{auto_added_text} and %{sent_text}
notice.user_made_admin                       %{which_user} has been made a coordinator.
notice.admin_rights_removed                  %{which_user}'s coordinator rights have been removed.
alert.duplicate_email                        %{which_email} is already in the group.
error.group_request_invalid_token            Sorry! This is an invalid token
error.group_request_contribution             Please select a category. This isn’t a commitment to pay, just useful information to help us design our model. Thanks!
error.group_request_already_accepted         Sorry! This invitation is invalid or has already been accepted.
error.group_request_already_verified         Sorry! The verification link you clicked has already been confirmed. If you haven't heard from us within 48 hours, get in touch: contact@loomio.org
error.position_not_updated                   Could not update position.
error.permission_to_invite                   You do not have permission to invite new members.
error.group_not_archived                     Group could not be archived.
error.contribution                           Please log in to make a contribution.
error.cant_state_position                    This proposal has closed.
error.cant_modify_position                   This proposal has closed.
error.cant_join_subgroup                     You cannot join a sub-group if you are not a member of the parent group.
date.formats.datepicker                      %d-%m-%Y
date.formats.for_another_year                %-d/%-m/%y
date.formats.for_this_year                   %e %b
time.formats.for_today                       %l:%M %P
attachment.error.too_large                   The file you tried to attach is larger than 50MB, please choose a smaller file.
errors.messages.email                        Not a valid email address
activerecord.errors.messages.blank           can't be blank
```