Add a check for SolidCache

[stevenchanin]

The stats returned by SolidCache are different from MemCache, so the existing check was failing.

Before we were seeing:

Default Collection
  cache: FAILED Error: 'undefined method `[]' for nil' (0.009s)

now we get

Default Collection
  cache: PASSED Cache is available (entries: 46/268435456, oldest: 331h, max: 1440h, 1 connections) (0.007s)

[emmahsax]

@stevenchanin All tests passed! Would you like to add something to the CHANGELOG.markdown? Something like this to lines 2-3 (but feel free to change the description text):

* Add a check for SolidCache cache check
  > stevenchanin: https://github.com/emmahsax/okcomputer/pull/15

In a few days, if I don't hear back, I'll just merge the PR and update the file with that above text after merge.

[emmahsax]

Thank you for the contribution! Your change will be in v1.19.0 when it's released! Hopefully that'll happen in the next month for sure.

[stevenchanin]

You're very welcome. Thank YOU for resuscitating the gem and moving it forward!

[emmahsax]

v1.19.0 has officially been released with this change!