Added a .tl file tokenizer and parser

A TLObject class has been added, as well as a method for tokenizen .tl files.
A TLObject can be created by simply calling `TLObject.from_tl(tl_line)`,
  this will tokenize the .tl line and return a new TLObject with all
  the required properties extracted.
Also added another method to load .tl files and yield TLObjects, including
  a SourceBuilder that can be later used to generate Python code.

parser/source_builder.py

@@ -0,0 +1,38 @@
+
+class SourceBuilder:
+    """This class should be used to build .py source files"""
+
+    def __init__(self, indent_size=4):
+        self.current_indent = 0
+        self.on_new_line = False
+        self.indent_size = indent_size
+
+        self.buffer = []
+
+    def indent(self):
+        self.write(' ' * (self.current_indent * self.indent_size))
+
+    def write(self, string):
+        if self.on_new_line:
+            self.on_new_line = False  # We're not on a new line anymore
+            self.indent()
+
+        self.buffer += list(string)
+
+    def writeln(self, string=''):
+        self.write(string + '\n')
+        self.on_new_line = True
+
+        # If we're writing a block, increment indent for the next time
+        if string and string[-1] == ':':
+            self.current_indent += 1
+
+    def end_block(self):
+        self.current_indent -= 1
+        self.writeln()
+
+    def __str__(self):
+        if self.buffer:
+            return ''.join(self.buffer)
+        else:
+            return ''