Issue 187: making the examples executable

[pengguanya]

• data creation script create_example_objects in /data-raw
• the data and R object are created by the script and stored in inst/extdata as .rds files
• the .rds files will be loaded in the example of main functions such as analyse and pool to make the example executable
• the package build/check time with and without executable examples are test and no significant differences are observed (less than 1 min difference and sometimes with example is even faster)