Match erl_first_files properly against all files needing
compilation and make sure the order of erl_first_files as specified in
rebar.config is preserved (rebar/rebar#445)

* Add a provider for the xref tool for running cross reference
  analysis on a project. Most of the code has been ported directly
  from the rebar2 rebar_xref module with some modification and cleanup
  to support testing.
* Port over the eunit test suite from rebar2, but convert it to
  common_test. The testing is the same, but now the
  erlang term output is examined to determine if the test run is successful
  instead of scanning the console output for the expected strings.

Moves ct_extra_params to the end of the generated ct_run command.
This allows users to pass commands to the underlying emulator
using -erl_args. The included rt test demonstrates that it is
possible to pass an addtional option to ct_run and -erl_args at
the same time. Finally, the test executes in regular and verbose
modes because rebar constructs the ct_run command differently in
verbose mode.

- Use `cover' with QuickCheck testing
- Reuse the `cover_*' rebar.config options
- Refactor cover-related code to separate module (`qc_cover_utils')
  for use with both `eunit' and `qc'

This reverts commit 3297ffec2c89c6b7135165b4bfaeaeb07167c33c, reversing
changes made to 0401debb3c.

attempt to emulate the behavior of
`erl -pa ebin -pa deps/*/ebin`

fix error messages and formatting issues of `rebar shell` by
shutting down and restarting the user subsystem in a mode more
hospitable to the shell than the simple user started when run
as an escript. emulate `error_logger` behaviour when the shell
is run via `erl`

add documentation of the shell command

limitations:

the erlang interrupt handler is not enabled when running as an
escript and there is no interface to re-enable it via erlang code.
this means `ctrl-c` will immediately exit the running process
unlike when running the shell via `erl`. `ctrl-g` is, however,
unaffected

the user subsystem is killed and restarted but not supervised. if
your code somehow relies on the user subsystem crashing and
restarting `rebar shell` may interfere with it's operation

Add my name to THANKS

* update files
* fix Dialyzer warning
* unconditionally enable info fil
* clean-up inconsistencies
* use term_to_binary compression
* use try...catch instead of case...catch...of
* do not write build info file if the graph is unmodified
* store info file as <base_dir>/.rebarinfo
* properly support list of compile directives
* fix regressions:
 - Fix a bug in handling of files to compile first.
 - If a file that is depended upon itself depends on other files, make sure
   those are compiled first. While at it, rename variables for correctness.
   Reported-by: David Robakowski
 - Make sure that FirstFiles has no dupes and preserves the proper order.
 - headers referenced via -include_lib() were not properly resolved to absolute
   filenames
 - .erl files found in sub dirs of src_dirs were not properly resolved to
   absolute filenames