Simplify opcode table generation
Use tellg instead of std::distance to get the file size.

Since std::distance increments the |begin| iterator until |end| is
reached, std::copy would not have any data left to read.
Additionally, this way the file doesn't have to be read if it's too
big for the chip's memory anyway.
Don't unnecessarily regenerate resource headers.
Merge pull request #9 from Ventero/opcode

Simplify opcode table generation
Merge pull request #10 from Ventero/fileread

Use tellg instead of std::distance to get the file size.
Merge pull request #11 from Ventero/depends

Don't unnecessarily regenerate resource headers.