use @proxy to prevent warnings
re-add return type for 'get context'
fix warnings and hints reported by analyzer
comment on noSuchMethod noop method
better handling of members with a prepending underscore
bug fix in `_ProxiedObjectTable.exitScope` : removeRange takes (start inclusive, end exclusive)

I was hitting a case where: (start = 22 , length = 38) ->
removeRange(22, 16)
RangeError: value 16 not in range 22..38
add test for inner scope exit
Merge pull request #105 from a14n/prevent-warnings

use @proxy to prevent warnings and fix 2 breaking changes