REPL: tab complete for Arrays #2316

Will be looking to land this long standing PR into v0.12. Will need to get it landed in io.js also.

nodejs/node-v0.x-archive#25819

The original issue:
"The tab complete for Arrays will
include any integer indexes. This is
suboptimal because obj.21 is not
valid syntax and a large array will
contain a very cluttered list."

Opening this as a tracking issue to make sure it lands.

/cc @Fishrock123