Refactor LCD mod -

- pixel coordinates are always unsigned
- use `for ... in range(...)` instead of `while ...`
Enable zinc tests
Remove dummy test
Add tests to CharIO
Add tests to LCD
Refactor LCD even further -

- fix hanging test by fixing signed/unsigned types
- get rid of C copypastaz and not needed mut vars
- more refactoring of while loops
Merge pull request #80 from errordeveloper/more_int_fixes

More int type fixes and tests for drivers

Reviewed-by: farcaller
Rakefile: Add documentation targets
Merge pull request #93 from bgamari/doc

Rakefile: Add documentation targets

Reviewed-by: farcaller
Fixes massive rust fallout based on https://github.com/hackndev/zinc/pull/94

 * to_str() is now to_string()
 * typaram doesn't have size specification any more
 * LIT_INT_UNSUFFIXED is now LIT_INTEGER and a bitch to parse
 * minor changes to CustomEmitter trait
Fix travis build for new non-rpath world
Merge pull request #95 from farcaller/fix-rust

Fixes massive rust fallout

Reviewed-by: farcaller
[pt::Builder] add error handling
Merge pull request #96 from errordeveloper/pt_error_handling

Added error handling in PT::Builder
Fixes for stm32f4 (close #81)
Merge pull request #97 from errordeveloper/fix_pr_81

Fixes for stm32f4

Reviewed-by: farcaller
Rake's build_docs action is now published
All PT API is marked experimental
Improved documentation for PT::Node
Added docs for PT test helpers