Fix #version method docs and some typos [ci-skip]

[ghousemohamed]

Summary

Made the doc for the #version method more consistent and fixed a few typos.

Other Information

[ghousemohamed]

@rafaelfranca I have a query related to the #version and #gem_version methods. Both the methods return the same value. Shouldn't there be a distinction between the two methods? For example, in railties, I can see that #version returns VERSION::STRING whereas #gem_version returns Gem::Version.new VERSION::STRING. Here there is a clear distinction between the two methods. Should this be the case for all other gems apart from railties?

[rafaelfranca]

No. The Rails version returns a string because of backwards compatibility. version is also in the other components there also for backwards compatibility since it doesn't add much value deprecate it. We could say version should return strings, but that will break someones code and it is not worth it.