chore: make it compatible with python 3.7

mostly due to outdated lxml version

Author: b1r3k

.python-version

@@ -1 +1 @@
-3.6.5
+3.7.1

.travis.yml

@@ -1,6 +1,10 @@
 language: python
+dist: xenial
+sudo: required
 python:
-  - "3.6.5"
+  - "3.6"
+  - "3.7"
+  - "3.7-dev"
 # command to install dependencies
 install: "pip install -r requirements-dev.txt"
 # command to run tests

requirements.txt

@@ -2,6 +2,6 @@ Markdown==2.6.11
 beautifulsoup4==4.4.1
 cssutils==1.0.1
 inlinestyler==0.2.1
-lxml==3.5
+lxml>=3.5,<=4.2.5
 pystache==0.5.4
 parse==1.8.2

setup.py

@@ -1,7 +1,7 @@
 import os
 from setuptools import setup, find_packages
 
-version = '0.3.1'
+version = '0.3.2'
 
 
 def read(f):