Merge pull request #40 from svnieuw/master

Add support for Source Map Revision 3.
Some autotools config
Add .gitkeep to m4 folder
Merge pull request #41 from jbussdieker/master

Some autotools config
Don't clean libsass if it's not specified
Allow older autoconf version to support brew package
Lower automake dependency too for homebrew
Need to remove parallel tests here and fix pkgconfig setup
Don't use pkgconfig
Change source map option from -g to -m or --sourcemap.
Add --load-path as alias for -I.
Add --style as alias for -t.
Add --line-numbers and --line-comments as aliases for -l.
Add --help as alias for -h.
Change input/output behavior to be similar to sass (Ruby).

- When no parameters are given, the input is read from stdin and the
  output is printed to stdout.
- When 1 parameter is given, it is interpreted as input path and the
  output is printed to stdout.
- When 2 parameters are given, the first one is used as input path and
  the second one is used as output path.
- When more than 2 parameters are provided, an error message is printed.
Merge pull request #43 from svnieuw/master

Update sassc after libsass unbalanced free() of source_map_file fix.
Merge pull request #44 from svnieuw/interface_rework

Change sassc interface to be more similar like Ruby sass.
Use getopt_long() instead of getopt_long_only() to parse arguments.

getopt_long() does not allow long options with a single '-'. It is a less
flexible than getopt_long_only(), but fixes the error message
"option '-l' is ambiguous" with MSYS on Windows.