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  superceded by the `Makefile`.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  superceded by the `Makefile`.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/.travis.yml

@@ -1,13 +1,14 @@
 language: go
+sudo: false
 go:
+  - 1.13.x
   - tip
 
-os:
-  - linux
-  - osx
-
 before_install:
-  - go get github.com/mattn/goveralls
-  - go get golang.org/x/tools/cmd/cover
+  - go get -t -v ./...
+
 script:
-  - $HOME/gopath/bin/goveralls -repotoken 3gHdORO5k5ziZcWMBxnd9LrMZaJs8m9x5
+  - ./go.test.sh
+
+after_success:
+  - bash <(curl -s https://codecov.io/bash)