* support list of repos for hex packages

repos are defined under the hex key in rebar configs. They can be
defined at the top level of a project or globally, but not in
profiles and the repos configured in dependencies are also ignored.

Searching for packages involves first checking for a match in the
local repo index cache, in the order repos are defined. If not found
each repo is checked through the hex api for any known versions of
the package and the first repo with a version that fits the constraint
is used.

* add {repos, replace, []} for overriding the global & default repos

* update to hex_core for hex-v2 repo support

This patch adds only single repo hex-v2 support through hex_core.
Packages no longer filtered out by buildtool metadata and the
package index is updated per-package instead of fetched as one
large ets dump.

* tell travis to also build hex_core branch

Includes an update to parse_trans on an OTP-21 friendly version

Also small output fix in rebar3 shell

cth_readable 1.4.0 supports the new logger interface from OTP-21, which
likely breaks compatibility with R16 builds.

It also includes a new compact interface, displaying output such as:

    ===> Running Common Test suites...
    %%% rebar_alias_SUITE: ......
    %%% rebar_as_SUITE: ...........
    %%% rebar_compile_SUITE:................................
    ............................
    %%% rebar_compile_SUITE ==> test_name: SKIPPED
    %%% rebar_compile_SUITE ==>
    {tc_user_skip,"compile:env_compiler_options/0 available"}
    ..
    %%% rebar_cover_SUITE: .............
    %%% rebar_ct_SUITE: ....................................

Allowing to display more tests within less screen space.
This mode has been added to the ct_readable option under the name
'compact' (now supporting true | false | compact), and has been made
default for rebar3.

Fixes some lager warnings since config changes

Eliminates a lager warning due to config format deprecation

This replaces all deprecated function usage by alternative ones based on
a version switch enacted at compile time, preventing all warnings.

This will likely introduce some possible runtime errors in using a
Rebar3 compiled on OTP-20 or OTP-21 back in versions 19 and earlier, but
we can't really work around that.

A bunch of dependencies have been updated to support OTP-21 without
warnings as well.

Get more up-to-date root certs. This was blocked for a while because
certifi wouldn't build on windows, but this is now fixed, with minimal
changes to the use case -- only a small change in the bootstrap script
is required.

The new certifi lib is also a few megabytes lighter than before, which
is good for rebar3.

This fixes the output of end_per_testcase crash notifications when the
test passes.

This also detect an issue of the kind with rebar_pkg_SUITE which is now
fixed.

Fixes an issue where some skipped test suites could end up misreported
as the previous suite. See
https://github.com/ferd/cth_readable/issues/10

relx ~> 3.22.0
erlware_commons ~> 0.22.0
cf ~> 0.2.2

Prior to this patch, the escriptize command flat out selected all
declared dependencies.

This patch instead looks at the app files and only includes the
dependencies of the top level app and the extra ones, avoiding to
package more apps than required.

This required a version bump on cth_readable as it mistakenly included
'syntax_lib' instead of 'syntax_tools' as a dependency.

This reworks the version and hash printing in the lockfile to minimize
diff changes:

- the version is on its own line so that the locks are mostly the same
  aside from the last line
- the hashes are each printed on one line with the package name for
  simpler diffing too.

latest mozilla bundles

The new version fixes parse transforms over OTP incompatibility that
would crash entire compile runs before.