CLN Pep8 on format.py
While looking at making a separate PR in format.py, I decided to first clean up the file and make it PEP8 compliant. I used 99 maximum-line-length per http://legacy.python.org/dev/peps/pep-0008/#maximum-line-length.

I also noticed that line 965 (in master) has a list comprehension that iterates through a non-instantiated variable (**row**):

``` python
for i in range(nrows):
    if truncate_v and i == (self.fmt.tr_row_num):
        str_sep_row = [ '...' for ele in row ]
        self.write_tr(str_sep_row, indent, self.indent_delta, tags=None, nindex_levels=1)

        row = []
        row.append(index_values[i])
        row.extend(fmt_values[j][i] for j in range(ncols))
```

By the time it has gone through the loop once, **row** is set, but it really should be instantiated ahead of the loop to be safe.

Additionally, I thought it might be useful to add a PEP8 test in test_format, just to make sure that future commits don't break PEP8. 

@jorisvandenbossche It think we have 80 char limit?
 @jreback @jorisvandenbossche let me know if you'd like me to convert this to 80 char. That shouldn't be a big deal. I'm more curious if you think adding a PEP8 test to lock in PEP8 on files as they get converted is a good idea. I think I've got all the places in the docs where dev requirements are discussed. I'll get that in a PR shortly.
 in theory once things are pepped the test should enforce it which is a good idea

but not sure if this will get spurious things as pull requests are made 
 On the 80 or 100 char limit, I don't think we have it specified somewhere? 

On the PEP8 testing in travis, I think this can be a good idea, but in such a case I think it should be a more general solution. Eg scipy and matplotlib run pep8 compliance tests in travis on the full code base, with some rules and some files ignored. It should also be better it showed what exactly failed (instead of just pass/fail). 
But that needs a seperate issue/mailing thread I think to discuss if we want this (that every PR has to be PEP8 compliant), and what rules we want to ignore for the pandas codebase.

See eg https://github.com/matplotlib/matplotlib/pull/1945 and https://github.com/matplotlib/matplotlib/blob/master/lib/matplotlib/tests/test_coding_standards.py
 @iwschris ok, so let's eliminate the pep8 test for now. And pls create another issue to setup the CI for this type of behavior @jorisvandenbossche mentioned.

No problem pepping things (but do as separate PR's one at a time after rebasing on master). so we can merge quickly.
 Will do!
 @jreback This should be good to go. I also created an issue for PEP8 Discussion here: https://github.com/pydata/pandas/issues/8317
 @iwschris thanks!
