Add run_opts to SSHKit.run with default empty list

[carterbryden]

This would allow us to do things like setup a custom capture function for messages while still getting to use the higher level contexts abstraction.

Description

Added a 3rd arg to SSHKit.exe that defaults to an empty list for run options, to be used with SSHKit.SSH.run underneath.

Motivation and Context

This issue reply explained how to use the underlying functions, but I'd really like to be able to keep using the conexts abstraction. This should let me do both.

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [x ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist

Haven't updated docs or tests because I think the existing ones already cover this.

• [ ] I have updated the documentation accordingly.
• [ ] I have added tests to cover my changes (with unit and/or functional tests).
• [ ] I have added a note to CHANGELOG.md if necessary (in the ## master section).