Put version handling into the helpers package so it can be used by many,
and split version and suffix to make it possible to calculate the next Hugo version.
On Windows the binary name is hugo.exe and running hugo version results in
this error:
GetFileAttributesEx D:\Dev\Go\gopath\bin\hugo: The system cannot find the file specified.
This fixes that error and allows the binary name to be something other
than hugo on any OS.
Added Version, CommitHash and BuildDate to hugolib/hugo.go and used it in build
Removed commitHash and buildDate from commands/version.go and used hugolib vars
Removed getDateFormat function from commands/version.go
Conflicts:
README.md
docs/content/templates/variables.md
