Fixes #46: Buffer.GetBytes could cause panics

[toqueteos]

Explanation: Buffer.GetBytes only checks that the input size is less than the total buffer size so if we are near the end of the buffer and we ask for more bytes than there are left but still less than the total buffer size it'll panic.

Example: suppose we have a buffer b of size 4. If we do two calls to b.GetBytes(3), the second one will panic because we are asking for the last byte and two more.

I've also removed some unnecessary endlines in buffer_test.go

EDIT: Added a longer explanation here.

[wirepair]

looks good to me.

[toqueteos]

Sorry I linked #42 instead of #46.

EDIT: I've fixed the commit message

[toqueteos]

Maybe instead of erroring out we should return all the remaining bytes and an error ErrEOB (end of buffer).

Another option is following io.Read's approach of returning the number of bytes read. But that's a breaking change on the API.

[gafferongames]

Thanks!