Gracefully handle files with invalid byte sequences

If a user accidentally linted a binary file (or file with some sort of
encoding problem), `scss-lint` would fail. This is frustrating when you
are linting a large project and due to a single invalid file your entire
lint run doesn't finish.

Modify the `Runner` and `Engine` classes to handle this case more
gracefully.

Fixes #59

Change-Id: Ice097f9f3fb3759f2eaef32812f8364014442341
Reviewed-on: https://gerrit.causes.com/32602
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>
Fix invalid encoding error handling for Ruby 1.9.3

Ruby 1.9.3 throws a different error when there is a problem with a
file's encoding. Handle this case manually.

Change-Id: I59c0b26ce51104c3f2a37f32017f0fca148769cc
Reviewed-on: https://gerrit.causes.com/32725
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>
Add reporter to get plain list of files

Use this if you want to open all files in your favorite editor. This
formatter outputs just the names of the files and makes it possible to
do something like: `scss-lint -f Files | xargs vim`

Change-Id: I64f17d14dab54a735882135484e66ab521b62a18
Reviewed-on: https://gerrit.causes.com/32723
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>
Add exclude option for individual linters

Add a new `exclude` option to linter configurations, allowing users to
disable linters for files matching a particular glob.

Change-Id: Ic77162cf2dab250aba1296c17a0dc05616892c4f
Reviewed-on: https://gerrit.causes.com/32733
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>
Prevent crash on config files with only comments

There was a bug where configuration files containing only comments would
crash `scss-lint`. Change `load_options_hash_from_file` to handle this
case gracefully.

Change-Id: I2e3a02704c84189e94e998b67d2f712abbf861be
Reviewed-on: https://gerrit.causes.com/32734
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>