Introduce for_all function

[Gab-km]

This Pull Request is to introduce for_all function for the issue #10.

This includes:

• for_all function, which is a subsutitute for Arbitrary and Arbitrary#property with API limited
• may_throw function to handle errors

This allows us:

• To create properties a little easier than we are writing now

To learn how to write properties with for_all, see the issue #10.

To handle errors with for_all, we write properties as following:

for_all(
  (('integer', {"max": 100}),),
  'This is your func.',
  may_throw(your_func, SomeErrorType)
)

[Gab-km]

@futoase Is there any problems in this PR? Tell me anything frankly please. 😉

[Gab-km]

@futoase Hello, my master. You've been staying away from this PR.
Very sorry if I am a nuisance, and I should go away from this nice product... 😞