Only run SCAN tests on recent redis version
Use ruby<1.9 compatible hash syntax
Merge pull request #378 from badboy/scan-command

Scan command, fixes tests and restores ruby<1.9 compatibility
Cleanup.
Explicitly skip tests that don't match the Redis version.
Fix requires to allow running a single test.
Style.
Expose SCAN command as an Enumerator
Expose HSCAN command as an Enumerator (#hscan_each)
Expose ZSCAN command as an Enumerator (#zscan_each)
Expose SSCAN command as an Enumerator (#sscan_each)
Only run *scan_each tests on redis > 2.7.105