Allow Ranges on Rash to match _all_ Numerics

Previously, it checked only for Integers; unfortunately,
that left Floats out, so passing in a float would cause
it to look it up normally.  This also changes the range
checking to `cover?` instead of `include?`.  Also
adds a line to a test to check for float availability.
Merge pull request #184 from medcat/rash-numeric-access

Allow Ranges on Rash to match all Numerics
Minor CHANGELOG update.
Bump up Rubocop to 0.24.1
Merge pull request #186 from petergoldstein/feature/rubocop_0_24_1

Bump up Rubocop to 0.24.1
Automatically require version.
Update CHANGELOG.md

regarding the changelog on [3.1.0](https://github.com/intridea/hashie/blob/v3.1.0/CHANGELOG.md#31-7252014)
the Pr #177 hasn't been merged with 3.1.0
Update CHANGELOG.md

add ':' to keep the same structure in the changelog