Allow button calls without a button name

* pulled the default value up from the DSL impl to the dsl
Fix require paths

For consistency and portability
Fix space before parenthesis
Move one more spec require to the spec_helper
fix double one comment
Fix showing manual
Don't clear  top_slot when clear is called, clear current_slot

* Changelog: bugfix
* @wasnotrice: might be important to note for/after the #759 merge
  ... sorry :(
* it has a change log right in here because the real purpose for
  merge commit etc. is yet another bug
inspect should not be private
Do not switch context to parent after clear/append

* switch to the current_slot that has been used before
* current_slot is set once in the beginning to make this
  work fully
* @wasnotrice: more possible merge headaches
* surprised this bug existed so long before being squashed
* fixes #756
spec the actual text of the button
Merge pull request #760 from shoes/button_without_name

Allow button calls without a button name

Changelog: improvement
Merge pull request #762 from shoes/clear

Fix slot clearing

- only clear current slot
- after clear, switch to previously current slot rather than parent

Changelog: bugfix
Merge #clear fixes from #762
Edit contexts, docstrings for consistency and clarity