TST: occasional sql failure
https://travis-ci.org/pandas-dev/pandas/jobs/218059636 (this of course worked when I restarted)

```
=================================== FAILURES ===================================
___________ TestSQLApiConn.test_warning_case_insensitive_table_name ____________
self = <pandas.tests.io.test_sql.TestSQLApiConn testMethod=test_warning_case_insensitive_table_name>
    def test_warning_case_insensitive_table_name(self):
        # see GH7815.
        # We can't test that this warning is triggered, a the database
        # configuration would have to be altered. But here we test that
        # the warning is certainly NOT triggered in a normal case.
        with warnings.catch_warnings(record=True) as w:
            # Cause all warnings to always be triggered.
            warnings.simplefilter("always")
            # This should not trigger a Warning
            self.test_frame1.to_sql('CaseSensitive', self.conn)
            # Verify some things
            self.assertEqual(
>               len(w), 0, "Warning triggered for writing a table")
E           AssertionError: 8 != 0 : Warning triggered for writing a table
pandas/tests/io/test_sql.py:944: AssertionError
============================ 10198 tests deselected ============================
===== 1 failed, 493 passed, 19 skipped, 10198 deselected in 163.26 seconds =====
```
