add go build for build errors (#180)

* add go build for build errors

* Add go build to doc and README

* Improvement for Go build

Go build works on package level, so copy over the other files
that belong to the same package to the temp folder as well.

* revert back to simple go build

* change gobuild script var name

ale_linters/go/gobuild.vim

@@ -0,0 +1,17 @@
+" Author: dzhou121 <dzhou121@gmail.com>
+" Description: go build for Go files
+
+function! s:FindGobuildScript() abort
+    return g:ale#util#stdin_wrapper . ' .go go build'
+endfunction
+
+let g:ale#util#gobuild_script =
+\   get(g:, 'ale_go_gobuild_script', s:FindGobuildScript())
+
+call ale#linter#Define('go', {
+\   'name': 'go build',
+\   'output_stream': 'stderr',
+\   'executable': 'go',
+\   'command': g:ale#util#gobuild_script,
+\   'callback': 'ale#handlers#HandleUnixFormatAsError',
+\})