llvm bot monitor: Shade every second bot in the tables

This makes it easier to read across a particular line.

While I'm here update the colspan to reflect the "T Since"
column that was added a while back.

Change-Id: I3256f93f679c2c5d77f1b7a1d1f2c42aad00235d
diff --git a/monitor/bot-status.py b/monitor/bot-status.py
index 5a54299..be7851c 100755
--- a/monitor/bot-status.py
+++ b/monitor/bot-status.py
@@ -19,6 +19,7 @@
 # The requests allows HTTP keep-alive which re-uses the same TCP connection
 # to download multiple files.
 import requests
+from textwrap import dedent
 
 from buildkite_status import get_buildkite_bots_status
 
@@ -161,22 +162,36 @@
   # Whether we use the fail favicon or not
   found_failure = False
 
+  temp.write(dedent("""\
+          <style>
+            /* Combine the border between cells to prevent 1px gaps
+               in the row background colour. */
+            table, td, th {
+              border-collapse: collapse;
+            }
+            /* Colour every other row in a table body grey. */
+            tbody tr:nth-child(even) td {
+              background-color: #ededed;
+            }
+          </style>"""))
+
   # Dump all servers / bots
   for server in filter(not_ignored, config):
     base_url = server['base_url']
     builder_url = server['builder_url']
     build_url = server['build_url']
-    temp.write("<table cellspacing=1 cellpadding=2>\n")
-    temp.write("<tr><td colspan=5>&nbsp;</td><tr>\n")
-    temp.write("<tr><th colspan=5>{} @ {}</td><tr>\n"
+    temp.write("<table border=0 cellspacing=1 cellpadding=2>\n")
+    temp.write("<tr><td colspan=7>&nbsp;</td><tr>\n")
+    temp.write("<tr><th colspan=7>{} @ {}</td><tr>\n"
                .format(server['name'], today))
 
     for builder in server['builders']:
-      temp.write("<tr><td colspan=5>&nbsp;</td><tr>\n")
-      temp.write("<tr><th colspan=5>{}</td><tr>\n".format(builder['name']))
+      temp.write("<tr><td colspan=7>&nbsp;</td><tr>\n")
+      temp.write("<tr><th colspan=7>{}</th><tr>\n".format(builder['name']))
       temp.write("<tr><th>Buildbot</th><th>Status</th><th>T Since</th>"
                  "<th>Duration</th><th>Build #</th><th>Commits</th>"
                  "<th>Failing steps</th></tr>\n")
+      temp.write("<tbody>\n")
       for bot in builder['bots']:
         temp.write("<tr>\n")
         try:
@@ -222,6 +237,7 @@
         else:
           temp.write(empty_cell)
         temp.write("</tr>\n")
+      temp.write("</tbody>\n")
     temp.write("</table>\n")
 
   temp.write("<link rel=\"shortcut icon\" href=\"{}\" "