Release v0.3.0-beta, from Devel branch

This pull request is made in order to update the master the next week. Please, discuss any change or improvement.

This new releases introduces the following summary:
- Some memory leaks and bugs solved.
- New methods to matrices.
- New ANN components.
- Added new datasets.
- Support of April-ANN as a Lua module, by compiling it as a shared library.
- Autocompletion via readline library for the standalone interpreter (package `require("aprilann.rlcompleter")`.
- Separation between ANN components and Backpropagation algorithm. The components compute gradients, and the `optimizer` class updates the weights.
- Added L1-norm regularization.