Improve some wording and correct some typos (#1336)

* Unification of words "behaviour" -> "behavior"

* Unify format

- `a`, `b`, `c` -> `A`, `B`, `C`
- D -> `D`

* Fix typo "againt" -> "against"

* Fix typo "Passanger" -> "Passenger"

* Fix typo "qeury" -> "query"

docs/docs/getting-started/simple-mode.md

@@ -50,7 +50,7 @@ This may be disabled by setting the `strip_whitespace` option in a Ransack initi
 
 ```ruby
 Ransack.configure do |c|
-  # Change whitespace stripping behaviour.
+  # Change whitespace stripping behavior.
   # Default is true
   c.strip_whitespace = false
 end

docs/docs/going-further/acts-as-taggable-on.md

@@ -67,24 +67,24 @@ When you're writing a `Ransack` search form, you can choose any of the following
 
 ### Option A - Match keys exactly
 
-Option `a` will match keys exactly. This is the solution to choose if you want to distinguish 'Home' from 'Homework': searching for 'Home' will return just the `Task` with id 1. It also allows searching for more than one tag at once (comma separated):
+Option `A` will match keys exactly. This is the solution to choose if you want to distinguish 'Home' from 'Homework': searching for 'Home' will return just the `Task` with id 1. It also allows searching for more than one tag at once (comma separated):
 - `Home, Personal` will return task 1
 - `Home, Homework` will return task 1 and 2
 
 ### Option B - match key combinations
 
-Option `b` will match all keys exactly. This is the solution if you wanna search for specific combinations of tags:
+Option `B` will match all keys exactly. This is the solution if you wanna search for specific combinations of tags:
 - `Home` will return nothing, as there is no Task with just the `Home` tag
 - `Home, Personal` will return task 1
 
 ### Option C - match substrings
 
-Option `c` is used to match substrings. This is useful when you don't care for the exact tag, but only for part of it:
+Option `C` is used to match substrings. This is useful when you don't care for the exact tag, but only for part of it:
 - `Home` will return task 1 and 2 (`/Home/` matches both `"Home"` and `"Homework"`)
 
 ### Option D - select from a list of tags
 
-In Option D we allow the user to select a list of valid tags and then search againt them. We use the plural name here.
+In Option `D` we allow the user to select a list of valid tags and then search against them. We use the plural name here.
 
 ```erb
 <div class='form-group'>

docs/docs/going-further/i18n.md

@@ -27,7 +27,7 @@ en:
       gt: greater than
       lt: less than
     models:
-      person: Passanger
+      person: Passenger
     attributes:
       person:
         name: Full Name

spec/ransack/predicate_spec.rb

@@ -368,7 +368,7 @@ module Ransack
         expect(@s.result.to_sql).to match /#{field} IS NULL/
       end
 
-      describe 'with association qeury' do
+      describe 'with association query' do
         it 'generates a value IS NOT NULL query' do
           @s.comments_id_not_null = true
           sql = @s.result.to_sql