Update requirements to allow latest versions of dependencies

[eyeseast]

Current reqs:

    "Flask==0.10.1",
    "Frozen-Flask==0.11",
    "Jinja2==2.7.3",
    "Markdown==2.4.1",
    "MarkupSafe==0.23",
    "PyYAML==3.11",
    "boto==2.38.0",
    "clint==0.4.1",
    "gnureadline==6.3.3",
    "google-api-python-client==1.3.1",
    "keyring==5.3",
    "oauth2client==1.5.2",
    "python-dateutil>=2.2",
    "requests==2.3.0",
    "sh==1.09",
    "wsgiref==0.1.2",
    "xlrd==0.9.3",

A bunch of these have later versions, and installing anything later breaks Tarbell.

[eyeseast]

We can probably pare this list down to just top-level dependencies. We don't need to have independent versioning of Jinja2 or MarkupSafe if Flask requires both.