Add ctags compatible --recurse alias

[dgsuarez]

Exhuberant Ctags has --recurse instead of --recursive, this just introduces --recurse=[yes|no] to the CLI to make the interface compatible (will avoid hacks with generic tags plugins in editors, in my case the well known https://github.com/ludovicchabant/vim-gutentags):

$ ctags --help | grep recur
  -R   Equivalent to --recurse.
  --recurse=[yes|no]

$ bundle exec bin/ripper-tags --help | grep recur
    -R, --recursive                  Descend recursively into subdirectories
        --recurse=[yes|no]           Alias for --recursive
        --all-files                  Parse all files in recursive mode (default: parse `*.rb' files)

Behaviour is the same as --recursive:

$ bundle exec bin/ripper-tags --recurse --verbose
Parsing file `test/test_ripper_tags.rb'
Parsing file `test/fixtures/_git/hooks/hook.rb'
Parsing file `test/fixtures/erb_template.rb'
...

Small difference is that it supports the --recurse=yes|no style like Ctags:

$ bundle exec bin/ripper-tags --recurse=no --verbose
ripper-tags: invalid option: needs either a list of files, `-L`, or `-R' flag

[mislav]

Looks good! Thank you