Update setuptools command option normalization

We were very naively "normalizing" options parsed and provided by
setuptools. This updates our handling to store the Option instance
from optparse so we can inspect the type, action, and option name for
more intelligent option normalization.

Closes #121

See merge request !52

We were very naively "normalizing" options parsed and provided by
setuptools. This updates our handling to store the Option instance
from optparse so we can inspect the type, action, and option name for
more intelligent option normalization.

Closes #121

Previously we were not reading output_file or enable_extensions from
user provided configuration files. The configuration option name
provided to config_options needs to be hyphenated in order for pep8 to
recognize and parse out the option correctly. Also, the destination name
needs to match the configuration option name that pep8 looks for
otherwise it will raise an unhandled KeyError exception.

Signed-off-by: Jason Myers <jason@jasonamyers.com>

Remove enabled extensions from `options.select`

When taking advantage of the --select flag for off-by-default
extensions, we neglected to take into account the fact that leaving the
extension names in the select list would cause different behaviour in
pep8. This should remedy this.

Related to GitLab bug #67

----

cc @joe-gordon0

See merge request !37

As noted in the code, setuptools 11.3 deprecated EntryPoint.load and
its require parameter. Starting with 11.3 the preferred way is use
EntryPoint.require and EntryPoint.resolve as necessary. Unfortunately,
those methods do not exist in all versions of setuptools. So we have
to check for them and use them when they're available. Otherwise, we
fallback to using EntryPoint.load with the require parameter.

Closes #59
Closes #90

This new flag is added so that off-by-default extensions can be enabled
without using --select which (currently) causes several problems with
pep8's rule engine. This also adds support to the --enable-extensions
flag to be specified as a multi-line config option in an appropriate
config file.

Closes GitLab #67