Add a test for namespace parsing

While namespacing is documented in the cache class there was no example
of its usage within the spec. This adds an explicit test to verify that
namespacing is applied when provided in the redis url.
Remove extended sleep spec

A multi-second expiration spec isn't necessary to verify expiration
functionality. The conversion of `1.second` and `1.minute` to second
values is the domain of ActiveSupport. The 61 second delay that was
present made me think the test suite was broken the first time I ran it.
Implement fetch_multi for parity with Rails 4.1

Attempts to be efficient by reading in a single block and writing all
missing values within a multi block.
Merge pull request #3 from sorentwo/namespace-spec

Add a test for namespace parsing
Merge pull request #4 from sorentwo/reduce-sleep

Remove extended sleep spec
Merge pull request #5 from sorentwo/fetch-multi

Implement fetch_multi for parity with Rails 4.1
Fix typo [ci skip]
Merge pull request #8 from 10io/patch-1

Fix typo