Provide default docs for callback implementations

This only triggers if there is no doc present and the module
has correctly declared @behaviour (in the correct spelling).
Merge pull request #88 from pminten/callback-implementations

Provide default docs for callback implementations
Use module_info instead of __info__

This fixes the :supervisor.__info__ not found bug.
Merge pull request #91 from pminten/use-module_info

Use module_info instead of __info__
removed unused alias
Merge pull request #95 from jwarwick/alias_warning

Removed unused alias
Update to latest Elixir
ignoring _build directory
Merge pull request #97 from jwarwick/gitignore

ignoring _build directory
more .gitignore cleanup
Merge pull request #98 from jwarwick/gitignore_cleanup

Removed ebin from gitignore
Updating bin/ex_doc code path from ebin to _build
Merge pull request #100 from jwarwick/cmdline_path

Updating bin/ex_doc code path from ebin to _build