setup.py: bump Pygments minimum version to 2.2.0

With pygments < 2.2.0, the markup_renderer doctest fails:

> python -m doctest kallithea/lib/markup_renderer.py
**********************************************************************
File "kallithea/lib/markup_renderer.py", line 184, in markup_renderer.MarkupRenderer.markdown
Failed example:
print MarkupRenderer.markdown('''
#!/bin/bash
echo "hello"
''')
Expected:
<table class="code-highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre>1
2</pre></div></td><td class="code"><div class="code-highlight"><pre><span></span><span class="ch">#!/bin/bash</span>
<span class="nb">echo</span> <span class="s2">&quot;hello&quot;</span>
</pre></div>
</td></tr></table>
Got:
<table class="code-highlighttable"><tr><td class="linenos"><div class="linenodiv"><pre>1
2</pre></div></td><td class="code"><div class="code-highlight"><pre><span class="ch">#!/bin/bash</span>
<span class="nb">echo</span> <span class="s2">&quot;hello&quot;</span>
</pre></div>
</td></tr></table>
**********************************************************************


To avoid having to manage multiple outputs from multiple versions, just bump
the lower version.

pygments 2.2.0 was released on Jan 22, 2017.