unified shell handling code
move shellescape to shell handling code
improved extra_grep
remove unneded array from debuger patter
Merge branch 'master' into feature/unified_shell_handling

Conflicts:
	lib/plugins/pre_commit/checks/coffeelint.rb
	lib/plugins/pre_commit/checks/scss_lint.rb
	lib/pre-commit/checks/grep.rb
Merge pull request #181 from jish/feature/unified_shell_handling

improved shell handling