make instructions on README have pandoc dependency installation requirement on macOS 10.14

[chrissimpkins]

Expected behaviour

Use of make according to installation instructions on repo README will complete without errors on macOS v10.14.1 where pandoc is not installed by default.

Actual behaviour

github.com/mrtazz/checkmake  master ✔                                    151d
▶ make
install -d .d
echo "checkmake: $(go list -f '{{ join .Deps "\n" }}' cmd/checkmake/main.go | awk '/github/ { gsub(/^github.com\/[a-z]*\/[a-z]*\//, ""); printf $0"/*.go " }')" > .d/checkmake.d
go build -ldflags "-X 'main.version=0.1.0-14-gff21564' -X 'main.buildTime=2018-11-30T16:50:39Z' -X 'main.builder=Chris Simpkins <git.simpkins@gmail.com>' -X 'main.goversion=go version go1.11.2 darwin/amd64'" -o checkmake cmd/checkmake/main.go
sed "s/REPLACE_DATE/November 30, 2018/" man/man1/checkmake.1.md | pandoc -s -t man -o checkmake.1
/bin/sh: pandoc: command not found
make: *** [checkmake.1] Error 127

Output of checkmake --version

checkmake  built at  by  with

go get executed on commit https://github.com/mrtazz/checkmake/commit/ff21564a952cb62b4632a0ba7637499bb8f775fc

Output of make --version

GNU Make 3.81

When pandoc installed with brew install pandoc the make execution completes with exit status code 0; however, the version information is missing the build date/time and builder:

github.com/mrtazz/checkmake  master ✔                                    151d
▶ checkmake --version
checkmake  built at  by  with