update README.md to version 0.7.5

version v0.7.4: update README.md

go.mod: update gomacro to 20210624153544, adds standard library symbo…

…ls defined in Go 1.12 and 1.13

go.mod: update gomacro to 20210316200708, fixes import of third-party…

… packages on Go >= 1.16

freebsd: if compiled with Go >= 1.14, support loading third-party pac…

…kages at runtime

(by updating gomacro dependency)

doc: update installation notes for Windows

use github.com/gofrs/uuid instead of github.com/satori/go.uuid; updat…

…e to latest gomacro

use GO111MODULE=on to import packages at runtime

ci: drop Go-1.10 and 1.9, add Go-1.13 and 1.12

really fix #174: previous fix broke some imports, including "fyne.io/…

…fyne/widget"