DOC: Add common error message to byte-ordering gotcha.

A friend of mine got tripped up by [this gotcha](http://pandas.pydata.org/pandas-docs/stable/gotchas.html#byte-ordering-issues). We document it well, but Googling the error message doesn't turn up our documentation, so it took him a lot of digging to get there.

This commit adds an example error message that byte-ordering issues raise, in hopes of making this easier to Google.