Raise error on insert into system collection.

Only if the collection is not system.users or system.indexes.

[ RUBY-492 ]
minor: moving away from .rvmrc, adding gitignore for .ruby-version
minor: merge should be called with parens here
RUBY-537 fixing behavior of strict, adding deprecation notice
improvement: limiting db#command calls for capped?, cleaning up init
improvement: clean-up of db, lots-o-improvements
Merge pull request #176 from mongodb/raise-error-on-system-insert

Raise error on insert into system collection.
RUBY-533 Split bulk inserts into many messages