Fixes offences of the following cops:
* Layout/SpaceAroundEqualsInParameterDefault
* Layout/SpaceAroundOperators
* Layout/SpaceBeforeBlockBraces
* Layout/SpaceInsideBlockBraces
`Pry::Platform` really looks like a helper and therefore should be defined as
one. Invoking `Pry::Platform` emits a warning now. Users are encouraged to use
`Pry::Helpers::Platform`.
Some tests are still failing, though. This commit fixes wrong usage of
temporary paths on Windows. Please, note: the `edit` command is working
well; the issue is in poor tests.
Prettify some ugly code in `spec/editor_spec.rb`.