Plugin changed to work with gulp 3.4.0 (stream handling needs to be implemented)

The plugin does not work with gulp 3.4.0. I changed the plugin to handle buffers and commented out the line "file = _.clone(file);" because it created an error and seams not to be needed.

Signed-off-by: uhunkler <urs.hunkler@unodo.de>
Update the dependencies to the latest component versions. Removed a bug I introduced with the changes.

When I ran the test I noticed that file needs only be changed when the front matter shall be removed. I removed the code again.

Signed-off-by: uhunkler <urs.hunkler@unodo.de>
Updated the mocha version. The test passes with the new version.

Signed-off-by: uhunkler <urs.hunkler@unodo.de>
Merge pull request #1 from uhunkler/master

Plugin changed to work with gulp 3.4.0 (stream handling needs to be implemented) (thanks @uhunkler)