Fix missing 'cd' that depended on cwd changes

Add pr2relnotes tool to generate release notes

bug fix: was using outer LevelsAcc variable in inner foldl

Fix links in README

update travis to test on 18 and 17.5

pass failing upgrade case where levels are increased

Fix reporting of error:undef exceptions

The wide-cast catching of undef errors would make it so any provider
calling an undefined function would be reported as a missing 'do' for
the provider.

This patch inspects the stacktrace to know if `Provider:do/1` is indeed
the missing callback, and reports the rest properly.

upgrade erlware_commons, bbmustache and relx

Only have the port cd, not rebar3 as a whole

don't run unnecessary code if hooks are empty list

handle http:// git deps in check fif upgrade needed

ensure necessary directories exist to compile mibs files

always close port when done with it. fixes #589

Add proxy support to bootstrap and rebar3. Enhancement #561.

Changed cases on robocopy so it uses variables in a better way

Robocopy fix for different behaviour when copying/moving files and folders

Run agent as current process & hibernate

This tries to reduce memory usage when running `rebar3 shell` by running
the agent in the current process (and avoiding to copy state
cross-boundaries), and using frequent hibernation after each run to
force a full GC and compaction of the current process.

wip: deps install refactor

Minor refactors