* Use set literals instead of set([...])
* Avoid list(sorted(...)) as sorted returns a list
* Replace dict() with dict literal

When we receive a SyntaxError, it is not guaranteed to have a token that
includes the physical line causing the issue. If it does not, we now
will avoid trying to determine the number of rows and columns that are
actually there and default to what the error tells us.

Closes #279

This adds two new methods to the BaseFormatter class:

- beginning
- finished

These will indicate when Flake8 begins and finishes processing a file.

Closes #251

Previously we added support so users can do:

    $ flake8 bin/executable

But this broke the fact that git hooks shouldn't check things like
reStructuredText doc files. This commit restores that functionality but
will cause bin/executable to be ignored in the git hook. This seems fair
since folks can amend their filename patterns to include it explicitly.

Closes #268

Handle SyntaxErrors in a slightly smarter way

SyntaxErrors are strange and mystical beasts. On top of the problems we
encountered previously in GitLab#237, it's now apparent that
SyntaxErrors can also occur across multiple lines (in fact, across the
rest of a file). In the event of a "multi-line" SyntaxError, we need to
determine what row to report and what the column number is.

For now, we're going to use the row number of the first line and limit
the column number to be less than the end of the line. It may not be
perfect, but it is slightly better.

Related-to #237  
Closes #259 

cc @arcanemagus

See merge request !151

By default, when discovering files for users, we use the filename
patterns to determine whether or not we should check that file. However,
when a user provides the path to a file, we should instead skip checking
the name against the filename patterns provided.

For example, in Flake8 2.6 this worked:

    $ flake8 bin/script.py
    $ flake8 bin/script

But prior to this commit only

    $ flake8 bin/script.py

works. This commit will skip the filename pattern check if the user
provides the path explicitly which allows

    $ flake8 bin/script

to work again as expected.

Closes #266

SyntaxErrors are strange and mystical beasts. On top of the problems we
encountered previously in GitLab#237, it's now apparent that
SyntaxErrors can also occur across multiple lines (in fact, across the
rest of a file). In the event of a "multi-line" SyntaxError, we need to
determine what row to report and what the column number is.

For now, we're going to use the row number of the first line and limit
the column number to be less than the end of the line. It may not be
perfect, but it is slightly better.

Related-to #237
Closes #259