add classes to next/previous month th cells in order to style them in…

…dividually.

lib/event_calendar/calendar_helper.rb

@@ -112,14 +112,14 @@ def calendar(options = {}, &block)
       cal << %(<table class="ec-calendar-header" cellpadding="0" cellspacing="0">)
       cal << %(<thead><tr>)
       if options[:previous_month_text] or options[:next_month_text]
-        cal << %(<th colspan="2" class="ec-month-nav">#{options[:previous_month_text]}</th>)
+        cal << %(<th colspan="2" class="ec-month-nav ec-previous-month">#{options[:previous_month_text]}</th>)
         colspan = 3
       else
         colspan = 7
       end
       cal << %(<th colspan="#{colspan}" class="ec-month-name">#{options[:month_name_text]}</th>)
       if options[:next_month_text]
-        cal << %(<th colspan="2" class="ec-month-nav">#{options[:next_month_text]}</th>)
+        cal << %(<th colspan="2" class="ec-month-nav ec-next-month">#{options[:next_month_text]}</th>)
       end
       cal << %(</tr></thead></table>)