Keyword argument support part 2

This does following changes:
- Now every send instruction will have the third (block name) param...

We can now support keyword arguments in user defined methods,
with/without default value are bot...

Fix #425, add #to_s for top level main object

Implement Hash#fetch

According to the Goby programming standard, function declarations should be in lexicographic order.

Float class (backend)

Add support for case expression

Implement Hash default

Fix integer parsing panic

Improved existing test cases; added new ones; aligned test values.

The panic would happen in regular circumstances, when passing a too big integer literal.

Ignore trailing whitespace in `String#to_i`, instead of immediately exiting

Example:

` 123`.to_i #=> 123, instead of 0

This is the longer and more readable implement...

Keyword argument implementation part 1

Implement Hash#delete_if

Implement Hash#select

Implement Hash#values_at

Implement the `:dig` method for `Hash` and `Array`

Implement Hash#any?

Hash#clear: clear the invoked hash

Conform the behavior to the same Ruby API, as the previous behavior (returning an empty hash wit...