Fix build

The build is currently failing during the installation of [email protected] with
an error like:

    File "..."
        from setuptools import setup, Extension, Feature
    ImportError: cannot import name 'Feature'

It appears that Feature was a deprecated API that was removed,
reintroduced, and then removed again [0].

Bumping the minor version of the dependency to 2.7 fixes this issue. The
release notes for [email protected] are available here:
https://github.com/pallets/jinja/blob/2.7/CHANGES#L4

[0] pypa/setuptools#2017 (comment)

Change-Id: I9cdf088c3bef8fbcbbdf540a5022a2341aab111f

requirements.txt

@@ -2,5 +2,5 @@ pid==3.0.4
 python-dateutil==2.2
 pymysql==0.6.2
 PyYAML>=3.10
-Jinja2==2.6
+Jinja2==2.7
 dnspython==1.16.0