Remove global plugins

install dep plugins & run provider hooks the same as shell hooks (Rereopen 316)

Fix ns help

modify `ct` provider to copy selected directories and compile them

alongside their source (ie, if `some_tests` is a directory that
contains test suites beams resulting from compiling them will be
placed in `some_tests` in the appropriate `_build` directory

update the dir used for upgrade deps to the new path under _build

impl shell completion

main module of a plugin just has to export init/1

Support namespace resolution in 'do' provider

cover enhancements

Fixes #306: help text consistency

fix clean all to use proper deps dir

re-export functions only used within rebar_utils that are also needed by...

fix congratulation message in README.md

Fix some dialyzer warnings

generate line by line coverage reports

Polish rough edges of 'new' provider

- Allow 'rebar3 help' to work and have it point to 'rebar3 help
  <template>'
- show a 'template not found' message when a template is indeed not
  found rather than crashing.

to the appropriate `_build` dir

eunit refactor and test suite