preliminary support for reading Mu Law encoded files...

needs cleanup and testing.
Fix an off-by-one indexing error in Mu-Law decompression
add a function to decompression A-law encoded files.
Use a single function to decompress A-law and Mu-law
Merge branch 'master' into myalaw

Conflicts:
	src/WAV.jl
Convert the mu-law and a-law integers to a double between -1 and 1.
Get mulaw and alaw working along with tests.

This change makes the alaw / mulaw feature functional.
Combine the functions to write alaw and mulaw samples

The functionality is very similar. Reuse the basic functions and
substitute the companding function.