ENH: parallel context

Currently don't have support for mapping yet, but we can submit system calls or function calls now via IPython. The latter may require state updates on the engines, which is feasible from the current context. It is likely that mapping will go in relatively easily. 

From the shell:

```bash
$ echo -e "profile\tdefault" >> ~/.qiime_config
$ echo -e "n_engines\t2" >> ~/.qiime_config
$ parallel start
```

From within Python:

```python
>>> from qiime.parallel.context import context
>>> context.submit_sync('hostname')
('rl1-1-220-221-dhcp.int.colorado.edu\n', '', 0)
>>> def foo():
...     return "bar"
...

>>> context.submit_sync(foo)
'bar'
>>> def foo(a):
...     return a**2
...
>>> res = context.submit_async(foo, 5)
>>> res.result
25
```

From the shell:

```bash
$ parallel stop
```
Sorry that's confusing, let me rephrase that, can you check that version works with the full Qiita stack?

Yoshiki Vázquez-Baeza

> On Oct 7, 2014, at 12:34 PM, josenavas <notifications@github.com> wrote:
> 
> In setup.py:
> 
> > @@ -256,6 +256,9 @@ def app_available(app_name):
> >        keywords=['bioinformatics', 'microbiome', 'microbiology', 'qiime'],
> >        platforms=['MacOS', 'Linux'],
> >        install_requires=['numpy >= 1.7.1',
> > +                        'click >= 1.0',
> Which other dependencies?
> 
> —
> Reply to this email directly or view it on GitHub.