Fix C+1y warnings from Clang.

warning: 'constexpr' non-static member function will not be implicitly
'const' in C++1y; add 'const' to avoid a change in behavior
[-Wconstexpr-not-const]
Merge pull request #61 from fahhem/master

Fix C+1y warnings from Clang.
doc: Update annotation code sample.
Fix missing annotations on fields (node translator) and methods, params, consts (capnp generator)
Merge pull request #62 from jmspiewak/master

Fix missing annotations
Fix containsInterval returning true when 'from' has underflowed
Merge pull request #63 from Ralith/fix-bounds-check

Fix bounds check passing for relative struct pointers with offsets that underflow
Merge branch 'master' into cmakeable
Merge branch 'cmakeable' into json