more array creation, argmin and argmax, and applyOverAxis functions

[xnought]

Array creation functions added:

• eye (ones down the diagonal and zeros everywhere else)
• tri (lower triangular 1s and 0s everywhere else)
• full (fills the array with specified fillValue)
• fullLike
• onesLike
• zerosLike

The ones with Like after take an array as input and create another array with the same shape. Just like numpy has.

closes #148

Basic functions added:

• argmax
• argmin

closes #147

New functions added:

• applyOverAxis (applies a basic aggregate vector function across an axis of an array. Please see the readme section with examples).

closes #54

Tests and Docs

New tests are added for every function mentioned above via Mocha *.spec.js tests. And all tests pass.

Examples for every function are also added to the documentation in the README.