Added Travis CI support and other new features

Unstable changes

• Added clustering and knn algorithms.
• Added ann.components.zca_whitening and ann.components.pca_whitening
  classes.
• Added stats.zca_whitening and stats.pca_whitening functions.
• Added packages autodiff and autodiff.ann, with automatic differentiation
  algorithms.
• Added ann.optimizer.quickprop algorithm, but stills untested.
• Gradients smoothing, based on weights sharing and bunch_size, is applied by
  trainable.supervised_trainer objects, not by the optimizer.
• Added ann.components.dropout class.
• Added ann.autoencoders.ae class, in order to factorize the SDAE code.
• Solved problems with CUDA compilation, but it stills not working because
  an error during cuMemAlloc.
• Class interest_points and layout algorithms (still in development).
• Added the geometry c++ class for working in to lines and point geometry.

API Changes

• Modified bootstrapping API in order to be similar with R: stats.boot() and
  stats.boot.ci().
• Added ann.optimizer.asgd for Averaged SGD optimization.
• Added trainable.qlearning_trainer for reinforcement learning tasks.
• Enhanced util.serialize and util.deserialize to accept functions as
  argument, allowing to serialize/deserialize over general streams.
• Added iscallable(...) function.
• Added utest package, for unit testing.
• Added methods to matrix which work with sparse matrices.
• Added class matrix.sparse.
• Added method m:toTabStream(file or gzfile) to matrix.
• Added operations math.log1p and math.logadd.
• Added operator % to Lua string metatable, allowing to do Python-like
  string formatting, and map-like substitutions.
• Added index matrix for min/max operations in matrix objects.
• Added serialize and deserialize Lua functions, in util package.

Bugs removed

• Solved bug which makes to load unitialized weight matrices when loading old
  trainable.supervised_trainer (without matrix.dict object).
• Solved bug at Matrix<T>::sliding_window which makes an early end of the
  iterator when window has an offset different of 0.

C/C++

• Added -lcblas option to build_release.lua and build_debug.lua.
• Added sparse CBLAS wrappers, for CUDA (not tested) and standard release.
• Added CBLAS wrappers for float, double, and ComplexF types.
• Added geometric parametrizer for off-line text preprocessing.
• Added dependency with liblapacke for PCA when not available MKL or MacOS X.

Other

• Added argument check at mathcore.block.* constructors.
• Travis is monitoring only master and devel branches, for push and
  pull-requests.
• Added travis compilation and testing platform for pull-requests.