Merge pull request #54 from spacecowboy/master

Update links to notebooks. Fixes 404-error.
fixes both #53 and #55. bumping version as it's an api change
Merge branch 'master' of github.com:CamDavidsonPilon/lifelines

* 'master' of github.com:CamDavidsonPilon/lifelines:
  Update links to notebooks. Fixes 404-error.
oops. That test sucked
acutally fixing #55, and tests
Update README.md
more robust
Merge branch 'master' of github.com:CamDavidsonPilon/lifelines

* 'master' of github.com:CamDavidsonPilon/lifelines:
  Update README.md
k real fixes. Don't use df.T syntax when T is a column in the dataframe
bumpnig
nuking cumulative_quadrature in favour of scipy.integrate, see #56
removing quadtrature, replacing with pure scipy. #56
bumping v
Add concordance index function

This commit includes a function for calculating Harrell's concordance
index, which can be calculated in R using 'hmisc'. The function is
implemented in Fortran, with a small Python wrapper. The reason for this
is that since calculating the C-index is a O(n^2) process, it quickly
becomes unacceptably slow with pure Python. Comparing a pure Python
implementation with the Fortran version, on arrays with length 1000,
Python required 434 ms while Fortran did it in 4.73 ms. So almost a
factor of 100 difference.

As a consequence of the addition of the Fortran module, the setup
script now utilizes numpy's setup function which will handle the
compilation of the native code.

In addition, a small unit test has been added. To be able to run the
unit tests, it is likely necessary to compile the native code first with:

    python setup.py build_ext --inplace

Signed-off-by: Jonas Kalderstam <jonas@kalderstam.se>