Merge pull request #3 from josdejong/develop

Merge pull request #163 from rjbaucells/develop
Bumped version number to 0.20.0-SNAPSHOT
Oops. Bumped version number to 0.20.1-SNAPSHOT
Fixed norm of vector bug when p is equal to zero
Merge pull request #165 from rjbaucells/develop

Fixed norm of vector bug when p is equal to zero
trigonometry hyperbolic functions
Merge pull request #166 from rjbaucells/develop

trigonometry hyperbolic functions
Updated history
Updated function overview
Fixed #169: Fixed functions `log`, `log10`, `pow`, and `sqrt` not supporting BigNumbers arguments resulting in complex numbers.
Added property `type` to all expression nodes in a node tree.
Minor simplification of function `mod`
Released version 0.21.0