Removed config instructions that no longer work
Corrected the rbx version names in the option descriptions
So far as I can tell, the default mode is now 1.9 (updated the readme)
Corrected a spelling mistake (follwing => following)
Removed reference to switching language mode
Refactor out method missing logic into single function

Also makes sure we store the original name as a seen name, so we
invalidate the cache when needed on these names.
Merge pull request #2528 from iainbeeston/update_build_instructions

Updated build instructions in the README to reflect what happens in ./configure
Adjust specs for Enumerable::Enumerator#initialize
Add specs on Enumerator#initialize for 2.0
Write spec fixture for Enumerator::Lazy
Write a spec for Enumerator::Lazy
Write a spec for Enumerable#lazy
Implement Enumerable#lazy
Write specs for Enumerator::Lazy#initialize
Implement Enumerator::Lazy#initialize
Fix Enumerator#initialize for 2.0
Write specs for Enumerator::Lazy#{map,collect}
Implement Enumerator::Lazy#{map,collect}
Write specs for Enumerator::Lazy#force
Implement Enumerator::lazy#force