Merge pull request python-metar#79 from akrherz/release_0_17

make 1.7.0 release of python-metar

Merge pull request python-metar#57 from akrherz/release_0_16

make 1.6.0 release of python-metar

Added release notes for v1.4 release

Updated to use str() method, rather than string()

1) Added debug (-d) and profiling (-p) options.

2) Silent mode (-s) is now completely silent.
3) Added quiet option (-q) which prints only parsing errors.

1) Changed the way the visibility group was parsed to allow better

   handling of units.  '9999U' and '7000M' are now accepted.
2) Added support for sky group of the form '///030///', indicating cloud
   height without coverage or type info.

Initial revision