TST: random html testing issues
I have seen these errors spuriously: https://travis-ci.org/jreback/pandas/jobs/79852164

but they go away when re-run...any ideas?

```
======================================================================
FAIL: test_to_html_truncate (pandas.tests.test_format.TestDataFrameFormatting)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/travis/build/jreback/pandas/pandas/tests/test_format.py", line 999, in test_to_html_truncate
    self.assertEqual(result, expected)
AssertionError: u'<div style="max-width:1500px;overflow:auto;">\n<table border="1" class="datafr [truncated]... != u'<div>\n<table border="1" class="dataframe">\n  <thead>\n    <tr style="text-al [truncated]...
Diff is 1759 characters long. Set self.maxDiff to None to see it.
======================================================================
FAIL: test_to_html_truncate_multi_index (pandas.tests.test_format.TestDataFrameFormatting)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/travis/build/jreback/pandas/pandas/tests/test_format.py", line 1115, in test_to_html_truncate_multi_index
    self.assertEqual(result, expected)
AssertionError: u'<div style="max-width:1500px;overflow:auto;">\n<table border="1" class="datafr [truncated]... != u'<div>\n<table border="1" class="dataframe">\n  <thead>\n    <tr>\n      <th></ [truncated]...
Diff is 2107 characters long. Set self.maxDiff to None to see it.
======================================================================
FAIL: test_to_html_truncate_multi_index_sparse_off (pandas.tests.test_format.TestDataFrameFormatting)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/travis/build/jreback/pandas/pandas/tests/test_format.py", line 1225, in test_to_html_truncate_multi_index_sparse_off
    self.assertEqual(result, expected)
AssertionError: u'<div style="max-width:1500px;overflow:auto;">\n<table border="1" class="datafr [truncated]... != u'<div>\n<table border="1" class="dataframe">\n  <thead>\n    <tr>\n      <th></ [truncated]...
Diff is 1877 characters long. Set self.maxDiff to None to see it.
----------------------------------------------------------------------
Ran 9032 tests in 947.494s
```
