Set window layout.

def initialize(self):
        """
        Set window layout.
        """
        self.grid()

        self.respond = ttk.Button(self, text='Get Response', command=self.get_response)
        self.respond.grid(column=0, row=0, sticky='nesw', padx=3, pady=3)

        self.usr_input = ttk.Entry(self, state='normal')
        self.usr_input.grid(column=1, row=0, sticky='nesw', padx=3, pady=3)

        self.conversation_lbl = ttk.Label(self, anchor=tk.E, text='Conversation:')
        self.conversation_lbl.grid(column=0, row=1, sticky='nesw', padx=3, pady=3)

        self.conversation = ScrolledText.ScrolledText(self, state='disabled')
        self.conversation.grid(column=0, row=2, columnspan=2, sticky='nesw', padx=3, pady=3)