Update dependencies

go get: upgraded github.com/lucasb-eyer/go-colorful v1.0.3 => v1.2.0
go get: upgraded github.com/mattn/go-runewidth v0.0.9 => v0.0.12
go get: upgraded github.com/mattn/go-shellwords v1.0.10 => v1.0.11
go get: added github.com/rivo/uniseg v0.2.0
go get: upgraded github.com/saracen/walker v0.1.1 => v0.1.2
go get: upgraded golang.org/x/sync v0.0.0-20201020160332-67f06af15bc9 => v0.0.0-20210220032951-036812b2e83c
go get: upgraded golang.org/x/sys v0.0.0-20201119102817-f84b799fce68 => v0.0.0-20210403161142-5e06dd20ab57
go get: upgraded golang.org/x/text v0.3.3 => v0.3.6