Fix 'make doc' issue on systems with node & nodejs

On systems with node installed as both 'node' and 'nodejs', 'make'
will evaluate 'which node nodejs' to include both the path to 'node'
and the path to 'nodejs', ultimatley psasing 'nodejs' as the first
argument to 'node' and throwing an error.

In order to fix this, and make 'make doc' run on systems with node
aliased to both 'node' and 'nodejs', I just added a 'grep' to select
the first of 'node' and 'nodejs' if both are defined.

Tested on Ubuntu 13.10 with GNU Make 3.81, GNU bash 4.2.45(1)-release
and Node.js v0.10.26.

Signed-off-by: Trevor Norris <trev.norris@gmail.com>
Changed documentation to clarify Correlation

Fix issue #73, 'What types of correlation does jstat do?'

Clarify Documentation:
- Which standard deviation estimator is calculated by stdev()
- Which variance estimator is calculated by variance()
- Which correlation coefficient is calculated by corrcoeff() (Pearson's
  Rho)

Signed-off-by: Trevor Norris <trev.norris@gmail.com>
Avoid NaNs in Beta distribution

Use the log form of the Beta function for generating the PDF for the
Beta distribution to avoid NaNs for large parameter values.

Signed-off-by: Trevor Norris <trev.norris@gmail.com>
Add calculation of arbitrary quantiles.

Signed-off-by: Trevor Norris <trev.norris@gmail.com>
Improve quantile calculation

Quantile calculation now more closely follows the scipy implementation.

Added further test and documentation.

Refactored test helper functions.

Signed-off-by: Trevor Norris <trev.norris@gmail.com>
Start keeping built files in repo

The files are small enough, and is more convenient for users that don't
want to have to build from scratch.
First steps to making the codebase more sane

There is a lot more to do, but made mention of the upcoming changes in
the README, and finished core.js.
Update tests with new format and stuff
Switch vector.js to new format
Update special.js
Add percentileOfScore()

Add function to calculate the percentile rank of a value in an array.

Signed-off-by: Trevor Norris <trev.norris@gmail.com>
Use assert.epsilon()

This is a method added to the vows API, but hasn't made it to the
documentation yet.
Finish updating spacing

Still a lot of style issues, but mostly getting there.
Fix instance pdf methods at 0

* Add  check for the gamma distribution instance vs. static pdf method
* Fix distribution instance pdf to allow 0.

Signed-off-by: Trevor Norris <trev.norris@gmail.com>
Add test for hypergeometric PDF

Adding a test that demonstrates how the hypergeometric PDF sometimes
returns NaN when trying to work with large populations and large
samples.

Signed-off-by: Trevor Norris <trev.norris@gmail.com>
Wrap up 0.0.3
Now working on 0.0.4
Improve Hypergeometric CDF and PDF

Add test that demonstrates how the hypergeometric PDF sometimes returns
NaN when working with large populations and large samples.

Add a test to make sure the hypergeometric PDF agrees with the basic
implementation for a range of parameter values.

Fix documentation header formatting.

Add more advanced algorithm for the hypergeometric CDF.

Change hypergeometric PDF to use the difference in the CDF to work
better with large parameter values.

Reviewed-by: Trevor Norris <trev.norris@gmail.com>
Fix t-dist confidence interval

The t-dist confidence interval should use n-1, not n.

Reviewed-by: Trevor Norris <trev.norris@gmail.com>
Working on 0.0.5