add typescript definitions

[disintegrator]

exports types for memoize, Cache, Serializer and Options.
The definitions are compatible with typescript 2.8 and above.

[codecov-io]

Codecov Report

Merging #67 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master      #67   +/-   ##
=======================================
  Coverage   97.29%   97.29%           
=======================================
  Files           1        1           
  Lines          37       37           
  Branches        8        8           
=======================================
  Hits           36       36           
  Misses          1        1

[disintegrator]

@caiogondim is there any action i need to take to get codeclimate to work?

[caiogondim]

Thanks for that.
Regarding Code Climate I added it as a test.
Will most probably disable it if it keeps giving us a headache.