constructive 1.1.0

Features:

• Implemented construction of R6 objects
• Implemented construction of zoo and xts objects
• Implemented "cbind" and "rbind" constructors for matrices
• Now there's no need to namespace opts_*() functions if the package is not
  attached, this mean we can call for instance constructive::construct(x, opts_tbl_df("tribble"))
  rather than constructive::construct(x, constructive::opts_tbl_df("tribble"))
• New classes and constructors can now be implemented in your package without
  importing the package (adding to "Suggests" instead)
• Added a hex logo

Fixes and improvements:

• Fixed a display issue in construct_diff()
• construct_clip() now shows a console message in addition to writing to the
  clipboard
• Improved support of data frames, tibbles, and data.tables regarding non syntactic, empty,
  NA or duplicate names
• Improved recycling in data frames
• Implemented support for dates in tribble() calls when calling construct(x, opts_tbl_df("tribble"))
• Improved support of classed matrices
• Fixed timestamp precision issue
• Improved support of "POSIXlt" class
• Improved encoding support
• Fixed construction of vectors with numeric_version(), package_version(),
  and R_system_version()
• Fixed construction of edge case calls like (`fun<-`)() or (`a b`)()
• Fixed construction of environments with NULL parents