3.3.1 (#529)

* makefile wip

* feat: adds Makefile

Adds a `Makefile` for managing build-related tasks.

* chore: updates dependencies

* chore: updates dependencies

* chore: updates bin scripts

- Removes `build_release.sh`
- Places deprecation notice in `build_devel.sh`, as its purpose has been
  superceded by the `Makefile`.

* chore: updates bin scripts

- Removes `build_release.sh`
- Places deprecation notice in `build_devel.sh`, as its purpose has been
  superceded by the `Makefile`.

* fix: Makefile

Makes several corrections and improvements to the `Makefile`:

- Previously, the `ifeq` rules were not behaving as intended, due to
  false assumptions regarding how `make` fundamentally behaves.
  Malfunctioning imperative-style programming has been replaced with
  declarative rules to repair this issue.

- Previously, all release executables were zipped after compilation. In
  order to spare non-Windows users from (possibly) needing to install a
  package to unzip the executables, all non-Windows binaries are now
  compressed with `gzip`. (Windows executables are still compressed with
  `zip`.)

- Removes a bit of needlessly verbosity in several rules and paths.

* chore: updates dependencies

* chore: bumps version to 3.3.1

vendor/github.com/mattn/go-isatty/README.md

@@ -1,7 +1,7 @@
 # go-isatty
 
 [![Godoc Reference](https://godoc.org/github.com/mattn/go-isatty?status.svg)](http://godoc.org/github.com/mattn/go-isatty)
-[![Build Status](https://travis-ci.org/mattn/go-isatty.svg?branch=master)](https://travis-ci.org/mattn/go-isatty)
+[![Codecov](https://codecov.io/gh/mattn/go-isatty/branch/master/graph/badge.svg)](https://codecov.io/gh/mattn/go-isatty)
 [![Coverage Status](https://coveralls.io/repos/github/mattn/go-isatty/badge.svg?branch=master)](https://coveralls.io/github/mattn/go-isatty?branch=master)
 [![Go Report Card](https://goreportcard.com/badge/mattn/go-isatty)](https://goreportcard.com/report/mattn/go-isatty)