Restrict property binder domain to values

Specifically, numbers and strings.  Previously, any non-null value would
be coerced to a string for the purpose of binding the property.  This
should avoid bugs when there are ephemeral type changes, which
thankfully have not yet been encountered in this case.
Add spec for `view`
Add a spec for omitting length from view()

nice to have
Spec for binding only() on set
Implement parent binder and with binder
Merge pull request #16 from montagejs/only-set

Fix only operator for Sets
Merge pull request #18 from montagejs/parent-binder

Implement parent binder
Merge pull request #17 from montagejs/bind-value-properties

Restrict property binder domain to values
Uprev Collections to 0.2.0
Update change log
0.2.14
More documentation

Adds documentation for:

-   parent scope, observer semantics, binder semantics, syntax
-   with scope, observer semantics, binder semantics
-   logical and and or observer, binder, binder semantics
-   default observer, syntax
-   defined observer, binder
-   concat semantics
-   last semantics
-   only observer semantics, binder semantics
-   every and some block binder semantics
-   polymorphic extensibility

Removes the grammar section. `grammar.pegjs` should suffice now.

Fixes references to the old content change listener interface, now range
change listeners.

Fixes range and map content syntax and binder semantics.

Adds to and qualifies the arguments of known operators in the syntax
description.
Merge pull request #21 from kriskowal/doc-scope

More documentation
Support polymorphic Scope nest method

Revisits the Scope implementation and nesting.  Scopes should be nested
with a method, which can in turn be overridden.  Scope should inherit
their properties when nesting, so they do not have to be passed forward
to nest.  Thus, the root scope can be extended to the advantage of all
child scopes.
Fix only operator for Sets

Sets don't have splice, but they do have clear and add, which will
suffice for the purposes of an `only` binder.
Restrict property binder domain to values

Specifically, numbers and strings.  Previously, any non-null value would
be coerced to a string for the purpose of binding the property.  This
should avoid bugs when there are ephemeral type changes, which
thankfully have not yet been encountered in this case.
Spec for binding only() on set
Implement parent binder and with binder
Uprev Collections to 0.2.0
Update change log