Ignore directories when recursively scanning

The call to `Find.find` was already recursing, but it was adding
directory names onto the `files` list, which in turn was causing the
Sass engine to choke trying to load a directory as a file.

Fixes #4.

Change-Id: I7c59ea3ff08410602d9e85459d8d615b49be9cb0
Reviewed-on: https://gerrit.causes.com/19252
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Greg Hurrell <greg@causes.com>
Add changelog

Change-Id: I013050435c24a141da542c70b8f96e6947c41540
Reviewed-on: https://gerrit.causes.com/19251
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Joe Lencioni <joe.lencioni@causes.com>
Fix shorthand_linter for most recent Sass gem

The internal structure changed between Sass versions. Previously, a
property such as:

    padding: 1px 1px 1px 1px;

Was stored as a `Sass::Script::String`, which the shorthand_linter was
explicitly sanity-checking. This changed to `Sass::Script::List`.
Fortunately, the `#to_s` returns the same thing, so the rest of the
linter works fine.

This drops the explicit class check for compatibility across versions,
letting duck-typing do its thing.

Change-Id: Ic9b1ce2d3a8ad48a284064fa24ac04fbd03612e4
Reviewed-on: https://gerrit.causes.com/19250
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Joe Lencioni <joe.lencioni@causes.com>
Only scan files with `css` or `scss` extension

Now that recursive directory scanning is working, it could be helpful to
pass a directory to `scss-lint` and have it only scan files that look
like they need to be linted.

Change-Id: I8eb2d49516b1514670f608b1f6c66c2e78615048
Reviewed-on: https://gerrit.causes.com/19253
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Joe Lencioni <joe.lencioni@causes.com>
Update release notes for version 0.5.5 (unreleased)

This will be released soon, hopefully after #1 is resolved and we have
XML formatting for Jenkins runs. I'm frontloading the work here to make
releasing said version easier.

Change-Id: I3d46ff87a337ce31584d4427f19f8c6c9a534a01
Reviewed-on: https://gerrit.causes.com/19255
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Aiden Scandella <aiden@causes.com>
Update readme to suggest simpler directory-scanning mode

Saving them bytes.

Change-Id: Ia6e70c0e98637193188849544bbe19533b477b71
Reviewed-on: https://gerrit.causes.com/19256
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Aiden Scandella <aiden@causes.com>
Update readme

* Linkify SCSS to its homepage
* Add brief contributing/testing instructions

Change-Id: I0ead69ef3791f5e5ed17976f1c94f28d184a9495
Reviewed-on: https://gerrit.causes.com/19261
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>
Improve option parsing to support params

Previously, the result of the `#parse!` call was essentially a no-op,
since it returned the items not consumed from `args`.

This adds an outer `options` hash, which the parser populates on
parsing. Presently, there are no options being read by the parser that
need to be persisted, but those are coming soon.

Additionally, this adds `--help` and `--version` flags.

While I was here, I extracted some of the lint-running code into a
private `#run` method, since the `#initialize` was getting a touch
unweildy.

Change-Id: I930e3c9210a14677f3d9558df6909114a1017ffc
Reviewed-on: https://gerrit.causes.com/19319
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Joe Lencioni <joe.lencioni@causes.com>
Adding support for outputting Lint XML
Adding tests for xml output