Some fixes

[mjholub]

I have removed some variable shadowing, commented out code and moved some global variables where they are needed. However there is one problem which I don't have the time to debug now, but which causes the program to segfault when it opens a file is this:

pkg/highlight/parser.go:322:7: SA5000: assignment to nil map (staticcheck)
                                                Groups[groupStr] = numGroups
                                                ^
pkg/highlight/parser.go:360:3: SA5000: assignment to nil map (staticcheck)
                Groups[group] = numGroups
                ^
pkg/highlight/parser.go:392:4: SA5000: assignment to nil map (staticcheck)
                        Groups[groupStr] = numGroups

This output was generated by golangci-lint, which can be also integrated into the project. See my setup for one of my project as some opinionated starter.