Add :history_size option to IEx
Fix v helper to work with new :iex_history format
Document :history_size option
Don't reverse v's output
s/less than 0/negative/
Extract history management in its own module
Make IEx helpers use inspect_opts where appropriate

For instance, the v helper would print the results in their entirety
ignoring the "limit" option.
Use just the process dictionary for keeping history
Minor code formatting fix
Implement the heuristics for garbage collection
Merge pull request #1121 from alco/iex-limit-history

Iex limit history