osx.aliases: Added Skype alias.
bash_it.sh: Added support for custom.plugins.bash and custom.completion.bash.
completion: Add completion/custom.completion.bash to .gitignore.
Merge pull request #288 from cceleri/hotfix_custom_script_support

Add support for `custom` scripts for all types, not just aliases
Update osx.aliases.bash

Fixed skype typo.
Merge pull request #289 from cceleri/feature_add_skype_alias

osx.aliases: Added Skype alias.