Fix checking for version as string

[rzane]

Was this broken, or is this just a proposed improvement?

[rocket-turtle]

No but it might break if Rails patch version gets higher than 9.

2.5.5 :001 > '5.2.3' >= '5.2.3'
 => true
2.5.5 :002 > '5.2.10' >= '5.2.3'
 => false

That would have been the case with Rails 4.2 -> 4.2.11.3