absinthe 1.5 support

[moperacz]

absinthe 1.5 changed schema pipeline and now it executes at compile time making use of rajska impossible

[gabrielpra1]

Tried to start working on it, but there seems to be a few issues with Absinthe 1.5 still. For example:

• meta no longer works for fields: absinthe-graphql/absinthe#927
• functions in meta are not working: absinthe-graphql/absinthe#928

[gabrielpra1]

Hey @moperacz, good news! With #30 and the release of Absinthe 1.5.4, this library is now compatible with the newest absinthe version 😄

Please let me know if you encounter any issues when upgrading, cheers!