feat(pipenv) Update client to use pipenv to manage dependencies.

Pipenv is the recommended tool for managing dependencies in modern Python
packages. It utilizes pip under the hood, adding version pinning like any
sane dependency manager.

Note that this change only impacts individuals working *on* lob-python; it
does not change the usage pattern/practice for consumers of the package.

.travis.yml

@@ -7,10 +7,12 @@ python:
 - '3.5'
 - '3.6'
 - 'pypy'
+before_install:
+  - pip install pipenv
 install:
-  - pip install -r requirements.txt
+  - pipenv install --dev
 script:
-  - nosetests  --with-coverage --cover-package=lob
+  - pipenv run nosetests  --with-coverage --cover-package=lob
 after_success:
   - coveralls
 notifications:

Pipfile

@@ -0,0 +1,15 @@
+[[source]]
+url = "https://pypi.python.org/simple"
+verify_ssl = true
+name = "pypi"
+
+[packages]
+requests = "*"
+
+[dev-packages]
+nose = "*"
+"flake8" = "*"
+coverage = "*"
+coveralls = "*"
+
+[requires]

README.md

@@ -142,12 +142,23 @@ There are simple scripts to demonstrate how to create all the core Lob objects (
 
 ## Testing
 
-Install all requirements with `pip install -r requirements.txt`.
+lob-python uses [Pipenv](https://docs.pipenv.org/) to manage development environments and dependencies.
+
+You install all the development requirements by running
+
+```shell
+$ pipenv install --dev
+$ pipenv shell
+```
 
 You can run all tests with the command `nosetests` in the main directory.
 
+```shell
+$ nosetests
+```
+
 =======================
 
-Copyright © 2013 Lob.com
+Copyright © 2013-2018 Lob.com
 
 Released under the MIT License, which can be found in the repository in `LICENSE.txt`.