Fix issue #157.
Some minor updates to the README
Use file-truename for all buffer-file-name calls
Build compilation database
Add a --get-compile flag for getting the command line for a file

This is an attempt to make it easier to use other tools, many of
which can use either a compilation database or the full command
line.
Hook in next-error, etc., to make iterating through matches more convenient
Add code for --get-compile messages
Use newlines, for convenience with process-lines
add tinfo
mb -> MB
Change ProjectsMap to use a std::map