Small markdown fixes for SLIP-0013 (#66)

slip-0013.md

-#SLIP-0013 : Authentication using deterministic hierarchy
+# SLIP-0013 : Authentication using deterministic hierarchy
 
 ```
 Number:  SLIP-0013
@@ -9,19 +9,19 @@ Authors: Pavol Rusnak <stick@satoshilabs.com>
 Created: 2015-03-12
 ```
 
-##Abstract
+## Abstract
 
 This document describes a method that is used for authenticating
 to various services such as websites or remote shells using a determinstic
 hierarchy.
 
-##Motivation
+## Motivation
 
 Using Deterministic Hierarchy for authenticating into systems is ideal,
 because the same concepts of easy backup that relate to backing up
 deterministic wallets can be applied to backing up user identities.
 
-##Service Identity
+## Service Identity
 
 Let's introduce the service identity. It consists of two elements:
 
@@ -37,7 +37,7 @@ b) index (32-bit unsigned integer)
 
 The index is used so one can generate more keys corresponding to the same URI.
 
-##HD Structure
+## HD Structure
 
 1. First concatenate `index` with the URI (`uri`). Use little endian for `index`.
 
@@ -51,7 +51,7 @@ The index is used so one can generate more keys corresponding to the same URI.
 
 6. Derive the HD node `m/13'/A'/B'/C'/D'` according to BIP32.
 
-###Worked example
+### Worked example
 1. `index + uri`=`0` + `https://satoshi@bitcoin.org/login`
 
 2. `sha256(index + uri)` = `d0e2389d4c8394a9f3e32de01104bf6e8db2d9e2bb0905d60fffa5a18fd696db`
@@ -66,7 +66,7 @@ The index is used so one can generate more keys corresponding to the same URI.
 
 See a [Python example](https://github.com/trezor/python-trezor/blob/ca45019918bc4c54f1ace899a9acf397c8f4d92f/tests/test_msg_signidentity.py#L27).
 
-##Challenge - Response
+## Challenge - Response
 
 Service issues the challenge consisting of three parts:
 
@@ -91,7 +91,7 @@ It's up to service operator to take this message and react in three possible way
 2. signature is valid, address/public key seen for the first time -> create user account
 3. signature is valid, address/public key known -> login to user account
 
-##References
+## References
 
 - [BIP-0032: Hierarchical Deterministic Wallets](https://github.com/bitcoin/bips/blob/master/bip-0032.mediawiki)
 - [BIP-0043: Purpose Field for Deterministic Wallets](https://github.com/bitcoin/bips/blob/master/bip-0043.mediawiki)