Avoid temporary file on linux (#10)

[maxnikulin]

• Use pipe process to avoid interference of pty processes in Emacs and xclip forks if -verbose option is not passed.
• Drop -verbose argument as redundant when pipe is used.
• Avoid explicit pattern for splitting command into arguments to allow any number of spaces in the variable value.
• Use split-string-and-unquote instead of plain split-string to allow both %t and \"%t\" variants of substitution.
• Perform substitution after splitting command into arguments as a safe option for the chance if some value contains spaces or quotes. (However it was necessary mostly for temporary file.)

[maxnikulin]

Feel free to decline this pull request, I do not insist.

The goal is to avoid overhead with pty and temporary files that are source of some problems.

[maxnikulin]

My personal concern is support of emacs-25.2 where make-temp-file does not have fourth argument