Update introduction.md for language corrections for the library-of-lu…

…ton exercise (#571)

exercises/concept/library-of-luton/.docs/introduction.md

@@ -1,20 +1,20 @@
 # Char
 
 `Char` is a data type in Crystal that represents a 32-bit [Unicode][unicode] code point.
-Their size makes so they are memory efficient, and also gives it certain properties that Strings don't have.
+Their size makes them memory efficient, and also gives them certain properties that Strings don't have.
 They are created using single quotes (`'`) and do only allow for one Unicode code point to be placed inside.
 
 ```crystal
 'a' # => 'a'
 'a'.class # => Char
 ```
 
-When working with Strings in Crystal is it quite common to work with Chars, since quite a few methods in the String class return Chars or takes Chars as arguments.
-For example, the [`String#[]`][index] method returns a Char, or the [`String#chars`][chars] method returns a collection of Chars.
+When working with Strings in Crystal it is quite common to work with Chars, since quite a few methods in the String class return Chars or takes Chars as arguments.
+For example, the [`String#[]`][index] method returns a Char, and the [`String#chars`][chars] method returns a collection of Chars.
 
 ## Incrementing / Decrementing
 
-Due to char being a 32 Unicode point do they support incrementing and decrementing, this makes it so if you have `'a'` so can you get `'b'` by adding one.
+Due to Char being a 32 Unicode point it supports incrementing and decrementing. For example, if you have `'a'` you can get `'b'` by adding one.
 
 ```crystal
 'a' + 5
@@ -36,8 +36,8 @@ There is also a method called [`Char#succ`][succ] which will return the next cha
 
 ## concatenation
 
-Since Chars is only meant to represent a 32-bit Unicode, can't 2 chars be concatenation.
-Thereby Chars can only be concatenated with Strings.
+Since a Char is only meant to represent a single 32-bit Unicode point, concatenation of 2 Chars is not allowed.
+Chars can only be concatenated with Strings.
 
 ```Crystal
 'a' + "bc"
@@ -47,7 +47,7 @@ Thereby Chars can only be concatenated with Strings.
 # => error: expected argument #1 to 'Char#+' to be Int or String, not Char
 ```
 
-## Properties methods
+## Properties, methods
 
 Crystal has a few methods that can be used to get information about a Char, like if it is a number or a letter, or if it is uppercase or lowercase.
 Here is a list of some of the methods, for a full list see the [Char API][char-api]:
@@ -65,7 +65,7 @@ Here is a list of some of the methods, for a full list see the [Char API][char-a
 
 ### Converting between code points and Chars
 
-Since Chars is a 32-bit Unicode point, so can you convert between Chars and code points (Int).
+Since Chars is a 32-bit Unicode point, you can convert between Chars and code points (Int).
 This can be done using the [`Char#ord`][ord] method which will return the code point of the Char, or the [`Int#chr`][chr] method which will return the Char of the code point.
 
 ```crystal
@@ -78,8 +78,8 @@ This can be done using the [`Char#ord`][ord] method which will return the code p
 
 ### Converting between types
 
-As with other data types so does Chars have a few methods that can be used to convert between types.
-The most common one is the `Char#to_s` method which will convert the Char to a String, but there is also the `Char#to_i` method which will convert the Char to an Int, And the `Char#to_f` method which will convert the Char to a Float.
+As with other data types, Chars have a few methods that can be used to convert between types.
+The most common one is the `Char#to_s` method which will convert the Char to a String. There is also the `Char#to_i` method which will convert the Char to an Int, and the `Char#to_f` method which will convert the Char to a Float.
 
 ```crystal
 'a'.to_s