Fix various typos

Fixes user-facing and non-user-facing typos

Found via `codespell -S "./vendor" -L ontext,rememberable,ridiculus,varius`

app/views/admin/registration_periods/_form.html.haml

@@ -1,5 +1,5 @@
 %p
-  Setup the time frame in which people can registrer to your conference
+  Setup the time frame in which people can register to your conference
 = form_for(@registration_period, url: admin_conference_registration_period_path(@conference.short_title)) do |f|
   .form-group
     = f.label :start_date

app/views/booths/_form.html.haml

@@ -18,7 +18,7 @@
     %abbr{title: 'This field is required'} *
     = f.text_field :submitter_relationship, rows: 5, required: true, class: 'form-control'
     %span.help-block
-      e.g. employee, comunity manager, etc
+      e.g. employee, community manager, etc
   .form-group
     = f.label :website_url, 'Website URL'
     %abbr{title: 'This field is required'} *

app/views/schedules/_schedule.html.haml

@@ -42,7 +42,7 @@
       }
   });
 
-  // hide the right and left controls when neccesary after moving the carousel
+  // hide the right and left controls when necessary after moving the carousel
   $('.carousel').on('slid.bs.carousel', '',
   function(){
     $(this).children('.left.carousel-control').show();

app/views/schedules/show.html.haml

@@ -43,7 +43,7 @@
     });
   });
 
-  // hide the right and left controls when neccesary after moving the carousel
+  // hide the right and left controls when necessary after moving the carousel
   $('.carousel').on('slid.bs.carousel', '',
   function(){
     $(this).children('.left.carousel-control').show();

app/views/shared/_object_changes.html.haml

@@ -12,7 +12,7 @@
         %th Updated Attribute
 
         %th{ class: "#{'hidden' if version.event == 'create'}" }
-          Prevous Value
+          Previous Value
 
         %th{ class: "#{'hidden' if version.event == 'destroy'}" }
           New Value