Add proper README.

README.md

@@ -1,6 +1,6 @@
 # lex
 
-TODO: Write a description here
+Use the liblex library to tokenize text.
 
 ## Installation
 
@@ -9,24 +9,35 @@ Add this to your application's `shard.yml`:
 ```yaml
 dependencies:
   lex:
-    github: your-github-user/lex
+    git: https://dev.danilafe.com/Chip-8-Wizardry/lex.git
 ```
 
 ## Usage
 
 ```crystal
 require "lex"
+
+# Create a lexer
+lexer = Lex::Lexer.new
+
+# Add tokens using their regular expression and value.
+# Tokens with larger value take higher priority.
+lexer.add_pattern(".", 0) # Matches any one character.
+lexer.add_pattern("ab+", 1) # Matches ab, abb, abbb...
+lexer.add_pattern("(ab)+", 2) # Matches ab, abab, ababab...
+lexer.add_pattern("ab*", 3) # Matches a, ab, abb...
+lexer.add_pattern("[a-d]", 4) # matches a, b, c, d
+lexer.add_pattern("[^a-d]", 5) # matches all chars but a, b, c, d
+
+# Lex some text
+tokens = lexer.lex "ab abb"
 ```
 
-TODO: Write usage instructions here
-
-## Development
-
-TODO: Write development instructions here
+An array of tuples of type `Tuple(String, Int32)` is returned.
 
 ## Contributing
 
-1. Fork it (<https://github.com/your-github-user/lex/fork>)
+1. Fork it (<https://dev.danilafe.com/Chip-8-Wizardry/lex>)
 2. Create your feature branch (`git checkout -b my-new-feature`)
 3. Commit your changes (`git commit -am 'Add some feature'`)
 4. Push to the branch (`git push origin my-new-feature`)
@@ -34,4 +45,4 @@ TODO: Write development instructions here
 
 ## Contributors
 
-- [your-github-user](https://github.com/your-github-user) Danila Fedorin - creator, maintainer
+- [DanilaFe](https://dev.danilafe.com/DanilaFe) Danila Fedorin - creator, maintainer