Preparations to Nim compiler v0.19.x

This release fixes some issues related to nim-lang/Nim#7889 and nim-lang/Nim#8838 introduced in new Nim compiler of version 0.19.0.

Another portion of bugfixes

• Fixed #8
• Fixed #9
• Fixed tests to reflect changes in upcomming Nim compiler 0.18.1
• Improved one little error message about the constants in object variants AST
• The repository has been moved to gitlab.com
• The documentation now is being built automatically on each release and is available on https://xomachine.gitlab.io/NESM/

Bugfixes for v0.4.0

• Fixed #7
• Fixed ignoring options in inline tuples

v0.4.0

Additions:

• Added the size option for the custom periodic structures deserialization.
• Added the sizeof options for the custom periodic structures serialization.
• Non-intrusive serialization support.
• Demo of the NTP packet serialization by NESM (thanks to @FedericoCeratto )

Changes:

• Changed syntax of options inside type declarations. (was a: int32 {option: value} but now a: int32 as {option: value}).

Fixes:

• Fixed the global context changing when options have passed to the toSerializable macro
• Fixed incorrect enum size when the {.size.} pragma is passed to its declaration.
• Cleanup from the deprecated functions usage.
• Little refactoring.