[Fab-user] Add feature : travis-ci pep8 check

[小明明]

Hi, all:

This is a great modification, but I think it is very necessary to.

When I read the source code and found that many pep8 norms. Moreover
travis-ci are not mandatory, but I think pep8 is the basic requirement, so
I added the feature and specification of the current source pep8 solved the
problem. Mainly contains the following problem:

1. imported modules but unused
2. it is not enough lines between code
3. redefinition
4. line too long
5. continuation line missing indentation or outdented
6. continuation line under-indented for visual indent

and so on.

But there are some problems such is needed, for example fabric.api, so
exhausted that situation I used `noqa`. Thanks