More robust shed-install script, install dependencies by default, improve logging

[mvdbeek]

• Use bioblend keyword arguments, this should help prevent the problem in https://github.com/galaxyproject/ansible-galaxy-tools/pull/34
• Better checks and error messages when an invalid tool has been specified
• Flip the install_tool_dependencies switch to skip_tool_dependencies, so that by default classic toolshed packages will be used
• Add an option to skip the changeset revision retrieved from an existing galaxy instance. This list could be used to update all installed tools (Except that we specifically skip tools that are already installed ...)

This addresses #9, #10 and #13

[mvdbeek]

@afgane @jmchilton I think this is ready from my side. Could we make a new release for ephemeris soon ?