Implement missing tests

How embarrasing…
Add error level for informational annotations
Use note level messages where applicable
Test go with GOPATH set

Go mandates the existence of this variable for Go code, see
http://golang.org/cmd/go/#hdr-GOPATH_environment_variable [golang] moved
Write Go output to temporary file

Writing output of the go compiler to /dev/null is not supported as go
checks for existence of the output and denies overwriting. Added a
helper for creating a temporary filename (without creating the actual
file) and sending output to this file. Flycheck takes care the file is
removed afterwards.
Improve temp file name generation

Rename the symbol to temporary-file-name to adhere to Emacs' naming
conventions, and create the temporary name in a sub directory of the
temporary directory to prevent symlink attacks.

Remove the extra function to generate temporary names.
Document temporary-file-name in the manual
Update changelog and credits
Use test-local process environment

We can just let-bind process-environment for single test cases.
[Fix #259] Merge branch 'gfrey-golang-dev-null-problem'

* gfrey-golang-dev-null-problem:
  Use test-local process environment
  Update changelog and credits
  Document temporary-file-name in the manual
  Improve temp file name generation
  Write Go output to temporary file
  Test go with GOPATH set
Improve error testing

Specify errors as for `flycheck-error-new-at' to get rid of our custom
error creation logic in test-helper, and directly compare the expected
against the real errors using `equal'.

That makes debugging of failed tests a lot easier!
Parse optional column information from go-build [#259]
Use standard display-buffer [#261]

Our custom display logic was a pretty nice mess, and broke other
packages such as popwin.
Merge branch 'master' into feature/info-level

* master: (49 commits)
  Use standard display-buffer [#261]
  Parse optional column information from go-build [#259]
  Improve error testing
  Use test-local process environment
  Update changelog and credits
  Document temporary-file-name in the manual
  Improve temp file name generation
  Write Go output to temporary file
  Test go with GOPATH set
  Simplify version info retrieval
  Remove dead test cases
  Update the changelog
  Fix headling in changelog
  get rid of Enhanced-Ruby-Mode
  Remove obsolete checker declaration macro
  [Fix #257] Close defface sexp
  Support alternative ruby modes
  Remove -property option from D checker
  [Fix #251] Handle abbreviated file names from luac
  Clarify licensing in HTML manual
  ...

Conflicts:
	doc/flycheck.texi
	flycheck.el
	test/builtin-checkers-test.el
Update Clang tests

Following 629773c
Fix test for info level
Merge pull request #215 from flycheck/feature/info-level

Add info error level
Refactor checker disabling in tests

Remove the corresponding argument from
flycheck-testsuite-should-syntax-check and instead add an explicit macro
to disable checkers for a certain code block
Simplify test resources for Ruby, Sh, TeX, Rst and D
Fix level for Pylint convention messages