Merge branch 'issue#6' into 'devel'

Issue#6: Review and organize S3 methods

This branch:
  - Review all generic S3 methods, those functions that has `.mcglm` sulfix.
  - Modifications predominantly were apply 72 column rule, add `@author`, `@method`, `@title` and `@name` in the documentation, add `\code{}` to occurrences of `mcglm`.
  - Ocurrences of `paste( , sep = "")` where replaced by `paste0( )`.
  - All the S3 generic functions were placed in one file named `mc_S3_methods.R`. Methods in general are small functions and they aren't the core of the package. Keep them in the same file reduces the number of files, is easier to find. Modifications in the function that produce a `mcglm` will, potentially, affect all generic methods, so the corrections must be applied in just one file.
  - Individual files containing one S3 methods were deleted.
  - The `qic.mcglm` where not placed in `mc_S3_methods.R`. Also, no `@method` were included in documentation. Its was treated as a regular function, not a method as the others. See CMT 
e406660a for details.
  - Put `README.Rmd` and `Examples/` in `.Rbuildignore`.

In the building process, there was a warning/note about the absence of the `ahs` object.

See merge request !4