Extend prompt patterns to match more default irb prompts in recent ruby, jruby, and under rvm

The following are examples of supported prompts:
    
    1.9.3p125 :001 >
    irb(main):001:0>
    1.8.7 :001 >
    1.9.3p125 :001 >
    1.9.3-p125 :001 >
    1.9.3-p125 :001 *
    1.9.3-p125 :001 '
    1.9.3-p125 :001 "
    1.9.3-p125 :001 /
    1.9.3-p125 :001 ]
    1.9.3-p125 :001 `
    jruby-1.6.7 :001 >
    
Rinari has long overridden `inf-ruby-prompt-pattern`, but it would
seem to make sense to improve the pattern at source, hence this pull
request.
    
There seems to be no technical reason for the previous difference
between `inf-ruby-first-prompt-pattern` and `inf-ruby-prompt-pattern`
-- this commit uses the same value for each, and IMO it would be worth
unifying the variables.
    
See https://github.com/eschulte/rinari/issues/26 for related discussion.