Update pip packages to latest versions

for reqs in `ls requirements`; do
    pur --skip django-tastypie,django,docker,elasticsearch,pyelasticsearch,commonmark,stripe,djangorestframework,mkdocs,django-allauth,django-filter,mercurial --requirement requirements/$reqs;
done

django-filter and mercurial added to the ignore list because incompatibilities.

requirements/lint.txt

@@ -1,7 +1,7 @@
 -r pip.txt
-astroid==2.0.1
-pylint==2.0.1
-pylint-django==0.11.1
+astroid==2.0.4
+pylint==2.1.1
+pylint-django==2.0.2
 pylint-celery==0.3
-prospector==1.0
+prospector==1.1.2
 pyflakes==2.0.0

requirements/pip.txt

@@ -3,8 +3,8 @@ pip==18.0
 appdirs==1.4.3
 virtualenv==16.0.0
 docutils==0.14
-Sphinx==1.7.6
-sphinx_rtd_theme==0.4.0
+Sphinx==1.7.7
+sphinx_rtd_theme==0.4.1
 
 Pygments==2.2.0
 
@@ -18,7 +18,7 @@ future==0.16.0
 django-tastypie==0.13.0
 
 django-guardian==1.4.9
-django-extensions==2.1.0
+django-extensions==2.1.1
 
 # djangorestframework 3.7.x drops support for django 1.9.x
 djangorestframework==3.6.4
@@ -32,7 +32,7 @@ jsonfield==2.0.2
 
 requests==2.19.1
 slumber==0.7.1
-lxml==4.2.3
+lxml==4.2.4
 defusedxml==0.5.0
 
 # Basic tools
@@ -57,7 +57,7 @@ pyquery==1.4.0
 # Utils
 django-gravatar2==1.4.2
 pytz==2018.5
-beautifulsoup4==4.6.0
+beautifulsoup4==4.6.3
 Unipath==1.1
 django-kombu==0.9.4
 mock==2.0.0
@@ -78,7 +78,7 @@ django-textclassifier==1.0
 django-annoying==0.10.4
 django-messages-extends==0.6.0
 djangorestframework-jsonp==1.0.2
-django-taggit==0.22.2
+django-taggit==0.23.0
 dj-pagination==2.3.2
 
 # Docs

requirements/testing.txt

@@ -4,10 +4,10 @@ django-dynamic-fixture==2.0.0
 
 # 3.6.1 and >3.2.5 is incompatible
 # with pytest-describe 0.11.0
-pytest==3.6.3
-pytest-django==3.3.2
+pytest==3.7.3
+pytest-django==3.4.2
 pytest-describe==0.11.1
-pytest-xdist==1.22.2
+pytest-xdist==1.23.0
 apipkg==1.5
 execnet==1.5.0