RVM support & rspec --init support

[AndyObtiva]

• Always generate RVM .ruby-version file defaulting to the same Ruby used to run juwelier command
• Support generating RVM files via the --rvm option, yielding .ruby-version and .ruby-gemset
• Avoid generating both .ruby-version and .ruby-gemset via the --no-rvm option
• Run bundle install after adding files to generated project when using --bundler
• Run rspec --init after adding files to generated project when using --rspec option (generating spec directory just like Jeweler did. This addresses my reported issue Not auto-generating spec/spec_helper.rb with --rspec option #13)
• Fix Juwelier's version in the version.rb file (will need another update when the next bump happens, please keep in mind)

(note: depends on #11 to pass the tests since it fixes the test suite, which was broken prior to my changes)

p.s. if you need maintainers, I’d be happy to help maintain Juwelier and Jeweler since I’ve been relying on since the mid 2000s and autoinstall for users of Glimmer DSL for SWT during scaffolding.

[AndyObtiva]

Just a quick note that one of my projects generated by Juwelier won a Fukuoka Ruby Award Competition 2022 Special Award:

https://andymaleh.blogspot.com/2022/02/glimmer-dsl-for-libui-wins-fukuoka-ruby.html

http://www.digitalfukuoka.jp/topics/187?locale=ja

The point I am trying to make is my projects not only rely on Juwelier, but require it to quickly scaffold new desktop applications.

It would be really great if this project would go back to being regularly maintained (which I thought was the whole point of splitting from Jeweler in the first place!).

Again, if you need help as an extra contributor, it is in my best interest to have this project continue to be maintained, and even florish! I do not like any of the competing products, and would much prefer using Juwelier (or Jeweler) instead.

Cheers!