change "Log In" to "Sign In"

because
http://www.designcult.org/2011/08/why-do-we-call-in-logging-in.html

app/views/layouts/application.html.erb

@@ -70,7 +70,7 @@
         <input name="username" type="text"     id="signin_username">
         <input name="password" type="password" id="signin_password">
         <input name="redirect" type="hidden">
-        <input type="submit" id="signin-button" value="Log In">
+        <input type="submit" id="signin-button" value="Sign In">
       </form>
     <% end %>
 

config/locales/client.en.yml

@@ -98,7 +98,7 @@ en:
     of_value: "of"
     generic_error: "Sorry, an error has occurred."
     generic_error_with_reason: "An error occurred: %{error}"
-    log_in: "Log In"
+    log_in: "Sign In"
     age: "Age"
     last_post: "Last Post"
     joined: "Joined"
@@ -487,7 +487,7 @@ en:
       complete: "If an account matches that username or email address, you should receive an email with instructions on how to reset your password shortly."
 
     login:
-      title: "Log In"
+      title: "Sign In"
       username: "Login"
       password: "Password"
       email_placeholder: "email or username"
@@ -853,7 +853,7 @@ en:
         success: "Thanks! We mailed out an invitation to <b>{{email}}</b>. We'll let you know when they redeem your invitation. Check the invitations tab on your user page to keep track of who you've invited."
         error: "Sorry, we couldn't invite that person. Perhaps they are already a user?"
 
-      login_reply: 'Log In to Reply'
+      login_reply: 'Sign In to Reply'
 
       filters:
         n_posts:

config/locales/server.en.yml

@@ -30,7 +30,7 @@ en:
   posts: "posts"
   loading: "Loading"
   powered_by_html: 'Powered by <a href="http://www.discourse.org">Discourse</a>, best viewed with JavaScript enabled'
-  log_in: "Log In"
+  log_in: "Sign In"
 
   via: "%{username} via %{site_name}"
   is_reserved: "is reserved"

config/locales/server.uk.yml

@@ -20,7 +20,7 @@ uk:
   posts: "дописи"
   loading: "Завантаження"
   powered_by_html: 'Створено за допомогою технології <a href="http://www.discourse.org">Discourse</a>, бажано переглядати з увімкненим JavaScript'
-  log_in: "Log In"
+  log_in: "Sign In"
   via: "%{username} через %{site_name}"
   is_reserved: "is reserved"
   backup:

spec/phantom_js/smoke_test.js

@@ -96,7 +96,7 @@ page.runTests = function(){
   });
 
   test("expect a log in button", function(){
-    return $('.current-username .btn').text() === 'Log In';
+    return $('.current-username .btn').text() === 'Sign In';
   });
 
   navigate("navigate to first topic", function(){