Update requirements to use pinned version of rlp

Author: ulope

requirements.txt

@@ -5,5 +5,5 @@ repoze.lru
 pbkdf2
 pycryptodome>=3.3.1
 scrypt
-https://github.com/ethereum/pyrlp/tarball/develop
+rlp==0.4.4
 https://github.com/ethereum/ethash/tarball/master

setup.py

@@ -32,7 +32,6 @@ def run_tests(self):
 # requirements
 install_requires = set(x.strip() for x in open('requirements.txt'))
 install_requires_replacements = {
-    'https://github.com/ethereum/pyrlp/tarball/develop': 'rlp>=0.3.9',
     'https://github.com/ethereum/ethash/tarball/master': 'pyethash'}
 install_requires = [install_requires_replacements.get(r, r) for r in install_requires]