Improve the link ordering for the main README and add a
"Getting Started" doc with basic usage information for new users.

Going forward, all documentation should be placed in the Documentation
directory in the root of the project. This switch allows maintainers to
approve updates to documentation before they are committed, as opposed
to the pre-existing wiki which anybody could modify.

Currently the Documentation directory includes docs on building, usage,
and minimal docs around the API. This is just the initial commit, and
documentation will continue to improve over time.

Some changes have been made (and will continue to be made) to `cmd/dlv` to
ensure we can auto-generate documentation for all commands from the
newly provided script `scripts/gen-usage-docs.go`, which can be invoked
via `go run scripts/gen-usage-docs.go`.

Additionally, version has been split into its own package. This was a
bit of housekeeping related to the changes made the `cmd/dlv`.

* Simplify
* Add links to wiki pages
* Add link to CONTRIBUTING doc
* Update description

Added help in commands

Add a couple of troubleshooting instructions for OSX users.

Allows compiling a test binary and debugging it.

Notable changes:
* OS X support
* Pure Go readline library
* Fixes issues debugged cgo enabled programs
* Substantial refactoring / code cleanup

Fixes #3 #29 #70

Currently Travis supports only Ubuntu 12.04 linux 2.6 VMs which are
terribly outdated, and trying to track down why it's hanging on Travis
but not on other similar VMs is more trouble than it's worth at the
moment.

Certainly another more appropriate and up to date CI solution should be
explored.