Add myself as module author

I am going to make a series of major changes, so it is in order to
clarify that I am to blame about anything evil.
Rename module from RPi::GPIO to Device::RPi::GPIO

This should help to keep namespace clean for future CPAN upload.
Add .gitignore listing autogenerated and vim temporary files
t/002_parms.t -> t/002_params.t: Fix typo in filename
t/002_params.t: Fix headline
Device::RPi::GPIO SYNOPSIS: Add some newlines for improved clarity
Device::RPi::GPIO USAGE: Change functions from head2 to list items

This is the common typography style for pods.
Device::RPi::GPIO pod: Put in the __END__ section
Device::RPi::GPIO USAGE: Rewrite both text and typography in better style
Device::RPi::GPIO DESCR., SEE ALSO: Elaborate, reference alternatives
Device::RPi::GPIO SEE ALSO: Fix nucwin's github link
Device::RPi::GPIO SEE ALSO: Add pasky's github link
Device::RPi::GPIO SYNOPSIS: Fix few bugs to actually match the API
Make errors fatal instead of just warning and returning 0 or undef

This is the common Perl convention. The caller may catch errors using
eval{}, but mostly it seems much better to actually do die completely.

croak is used if the error was caused by parameter validation to die
from the caller's perspective.
t/002_params.t: Adjust for new reality when constructor will happily die
Rewrite error handling for better flow, mainly use the 'open or die' idiom
t/002_params.t: Report the reason why the constructor died
Rename validate() to _map_channel(), move definition below public functions
Remove now-superfluous 'return 1' statements
README: Rewrite based on basic CPAN template

Simply copied perldoc output means synchronization issues. Rather list
just the DESCRIPTION text and additionally some build and copyright
information.