No utility functions; new aliases

Utility functions were removed as they are considered to belong in other
packages, e.g. dplyr.

Aliases are added to make some R operators more pleasant to use in
chains.

Rare bug in the pipe operator fixed.
Update README.md
Updated to evaluate LHS; update alias names. Few new aliases.

Used the newest version of %>% which evaluates LHS.

Added aliases, and tried to find better names.
Better handling of lhs.

Now lhs is handled better to accomodate evaluation, and when possible
preserving the call without breaking e.g. some of the dplyr
functionality. In these cases, __LHS is used as previously.

The readme is also updated.
Few fixes, anonymous functions.

Fixes as suggested in pull request. Added the possibility of using
anonymous functions and primitives. This also fixes the issue of e.g. of
dplyr replacing the name with a function object before pipe evaluation,
e.g. in mutate(iris, test = Sepal.Length %>% as.character)
minor fix wrt evaluation of anonymous functions.
Tidying of checks made on rhs.
Includes tests and a few more aliases.
update of travis file.
travis and tests - attempt 2
Merge branch 'master' into bruyere. Closes #4