Fix Enumerable.from() returning non-concurrent-safe enumerables in some cases.

One of the types produced enumerables in Enumerable.from() would share a
backing enumerator between all enumerators it generated. This caused
improper behavior when two enumerators from the enumerable were created
and evaluated concurrently.
Fix Tabs/Spacing
Merge pull request #5 from ProdigySim/fix-shared-enumerator

Fix Enumerable.from() returning non-concurrent-safe enumerables