Add tests to validate written image files
Add tests for writing binary PGM and PPM
Implement writing of binary PBM
Fix file mode
Split code into separate files
Fix README: 1.8.7 not supported
Rename 'test_read.rb' to 'test_pnm.rb'
Remove unused constants from Rakefile
Redefine 'to_s' as alias for 'info'
Improve documentation
Set maxgray value to 1 for PBM
Add Parser class and tests
Enable reading of all ASCII image formats
Add Converter class and tests
Enable reading of all binary image formats
Support images with comments
Improve documentation and update README
Improve tests for Image class
Fix reading/writing of binary data including CRLF
Document reading from and writing to an I/O stream