GeezerVison

Master to Devel Merge post v3.4.3 Release

This change also includes the fixes for currently missing documentation
and crate level documentation.

Earlier to this change, documentation was generated using the
command `cargo doc`. However, this has one drawback - when external
markdown files were used, additional set of commands had to be run
using `rustdoc` tool to generate the html files corresponding to
the md files. With this change, `generate_docs.sh` bash script will
handle those intricacies of running `cargo doc` followed by execution
of `rustdoc` for external md files.

This change adds the following tutorials to the documetation.
* Getting Started with ArrayFire
* Introduction to Vectorization
* Array and Matrix Manipulation
* Indexing
* Configure ArrayFire Environment

Remove rustc_serialize in favor of Serde crate

Add tutorials with examples to Documentation

The Array objects used by Indexer objects were not properly
incrementing the reference count. This led to memory corruption
and undefined behaviour which is fixed now.

starting commit d558748 rustc-serialize
has been replaced in favor of serde. Serde requires rust 1.15.1. Thus,
README has been updated reflecting the same.

Bug Fixes

Currently, only Seq and Array implement the Indexable trait.
Earlier to this change, there was no proper lifetime specification
for Indexer struct and Indexer::set_index method to enfore borrow
checking. This should be fixed now.

This issue doesn't happen on Windows and Linux.

Creating an Array from `&[]` directly instead of creating a vector
first and then borrowing a slice is causing crash on OSX platform.

This removed the need to impl unsafe Send & Sync traits for
Callback type.

Also updated the error handler test to be more rusty.