Modifying bak plugin tests to use fish spec

Do not add test/spec files to function path in _prepend_tree.

Make sure to exit with 0 of 1 when reloading the framework

run all tests, including plugins tests, on travis

Adding travis badge

❯❯❯ Complete overhaul of brand new Oh-My-Fish `fish-spec` test framework.

+ Add documentation and examples.
+ Add new functions to interact with the framework:
  + spec.eval - eval a function by name and echo its description field
  + spec.functions - prints functions currently in scope that match the key glob
  + spec.log - log a message / test result
  + spec.run - run suite of tests
+ Rename list.erase to erase.

Add travis support via .travis.yml and bash bootstrap script.

Improve install.fish

  + Non-interactive terminals, e.g., skip launching fish when
    running tests automated, etc.
  + Non-git-based installations. If git is not found, download
    via curl HTTP GET download request.
  + Installing forks of the framework.
Also:
  + Improve documentation.
  + Fix bug in un escaped backslash causing incorrect syntax
    coloring after the ASCII fish logo.

+ Extend to support any number of items and/or lists.
+ Add --from option.