Add the csympy package

It seems to build and works just fine. Here is how to test it:
```
$ conda create -c certik -n x3 csympy
Fetching package metadata: ...
Solving package specifications: .
Package plan for installation in environment /scratch/miniconda/envs/x3:

The following packages will be downloaded:

    package                    |            build
    ---------------------------|-----------------
    csympy-0.1                 |       np18py27_0         482 KB
    gmp-5.1.2                  |                2         602 KB
    ------------------------------------------------------------
                                           Total:         1.1 MB

The following packages will be linked:

    package                    |            build
    ---------------------------|-----------------
    csympy-0.1                 |       np18py27_0   hard-link
    gmp-5.1.2                  |                2   hard-link
    numpy-1.8.1                |           py27_0   hard-link
    openssl-1.0.1h             |                0   hard-link
    python-2.7.8               |                0   hard-link
    readline-6.2               |                2   hard-link
    sqlite-3.8.4.1             |                0   hard-link
    system-5.8                 |                1   hard-link
    tk-8.5.15                  |                0   hard-link
    zlib-1.2.7                 |                0   hard-link

Proceed ([y]/n)? 

Fetching packages ...
csympy-0.1-np1 100% |################################| Time: 0:00:00 946.15 kB/s
gmp-5.1.2-2.ta 100% |################################| Time: 0:00:00   1.15 MB/s
Extracting packages ...
[      COMPLETE      ] |##################################################| 100%
Linking packages ...
[      COMPLETE      ] |##################################################| 100%
#
# To activate this environment, use:
# $ source activate x3
#
# To deactivate this environment, use:
# $ source deactivate
#
$ source activate x3
discarding /scratch/miniconda/bin from PATH
prepending /scratch/miniconda/envs/x3/bin to PATH
(x3)$ python
Python 2.7.8 |Continuum Analytics, Inc.| (default, Jul  2 2014, 18:08:02) 
[GCC 4.1.2 20080704 (Red Hat 4.1.2-54)] on linux2
Type "help", "copyright", "credits" or "license" for more information.
Anaconda is brought to you by Continuum Analytics.
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>>> import csympy
>>> csympy.__file__
'/scratch/miniconda/envs/x3/lib/python2.7/site-packages/csympy/__init__.pyc'
>>> from csympy import var
>>> var("x y z")
(x, y, z)
>>> from csympy import var, sin
>>> sin(x*y).diff(x)
cos(x*y)*y
```
Why don't you merge this now. It works, and we can improve upon this with further PRs.