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.

Add msg plugin. The technicolor message printer.

Add notes in comments about escaping.

  + msg.util.get.color.fish
  + msg.util.random.color.fish
  + msg.util.set.color.fish
  + msg.util.str.get.fish
  + msg.util.str.has.fish

 + Print messages with style and color easily. Supported styles below:

     _text_                 Bold
     __text__               Underline
     ___text___             Bold and Underline
     `$variable`            Apply @<styles> to $variables
     /directory/            Directories
     [url]                  Links
     \n                     Line Break
     \t                     Tab Space

 + Recognizes 256 different color names and special @random @light @dark @error and @success labels.
 + Included also is `msg.ask` to print a message with `msg` and wait for y/n input. Returns true on y\*.

[feat-import] + import command, ⁑ bad wildcard expansion bugfix in _prepend_tree.

To import plugins or load themes:

 + import plugins/<plugin>
 + import plugins/{dpaste,cask} themes/bobthefish

Note: Plugins/Themes can be in either `custom/plugins`, `custom/themes` or `$fish_path/plugins/`, `$fish_path/themes/`.

+ All `.load` files inside custom are sourced as usual.

+ Only set plugins set in `$fish_plugins` as imported. Works whether they are in `$fish_path` or `$fish_custom` as expected. The same for plugins.

+ `$fish_function_path` is not polluted.

Add new `import` command for plugins,  simplifiying intial configuration setup in `oh-my-fish.fish`. Fix incorrect wilcard expansion bug in `_prepend_tree` and other typos in comments.

Function _prepend_path allowing multiple paths to be specified at once

Fix issue with rbenv plugin where some rbenv commands fail

Use rbenv fish integration, if available.

Fix rbenv "supports fish" logic.

adding local variable flag and setting the variable if java home isn't
taken care of in the first if check.

For some reason there were different tab widths for this bottom
section, unifying to what the top was at -- 2 spaces.

binaries, this fixes that.

This also sets JAVA_HOME (only tested on OSX).