Adding mendelian error code

Uses map and zip in leiu of loop.
Now assumes biallelic, diploid. In theory extensible to polyploid multiallelic, but too impractical for the moment.

Added test script run with nosetest test/ from the root dir.
Added benchmark script, run with python benchmark/benchmark_ped.py

for 1m variants, runs in approx 6 minutes for 10 samples. The more heterozygotes the slower it runs.
pep8 compliant
pep8 compliant
Refactoring mendelian error function.

Now all as numpy array operations

TO DO: remove old map function
New tests, fixed bug in homref vs homalt

Added new multivariant test.

Moved benchmark code to src

Fixed bug where had forgotton to index in the homref vs homalt case
Merge pull request #45 from hardingnj/master

Adding mendelian error code