Support for the upstream keybinding configuration variables

[wshanks]

How do you feel about supporting the keybinding variables used by upstream fzf as described here? Mainly, I am thinking of FZF_CTRL_T_OPTS and FZF_CTRL_R_OPTS.

For what it's worth, I mainly want this to override the --reverse in fzf_insert_history() because I am used to the default behavior of the bash keybindings that don't use --reverse.

[laloch]

Yes, you're right once again. I'm thinking about this change together with replacing all the configuration variables with upper-case versions since I adopted the project.
Maybe it's the time for some serious refactoring and for major version bump.