Fix search input margin

Before: https://www.dropbox.com/s/ppif4opa904m91k/broken_search2.png

After: https://www.dropbox.com/s/bxy065pzch39bg1/broken_search.png

Currently, the margin of the search input messes up the border line.

flask_admin/static/admin/css/admin.css

@@ -31,6 +31,10 @@ form.search-form .clear i {
     margin: 2px 0 0 0;
 }
 
+form.search-form div input {
+    margin: 0;
+}
+
 /* Filters */
 table.filters {
     border-collapse: collapse;
@@ -108,4 +112,4 @@ table.filters {
 
 .list-checkbox-column {
     width: 14px;
-}
\ No newline at end of file
+}