Update .gitignore to ignore same files as in veritas project
Fix code formatting in spec/rcov task
Add spec for Virtus::Coercion::Time.to_time
Add spec for Virtus::Coercion::DateTime.to_datetime
Add spec for Virtus::Coercion::Date.to_date
Fix code formatting for rcov

* This is one of the few cases where I will adjust the code formatting for rcov,
  because I know of no way to allow this code to be covered using the old
  formatting.
Add spec for Virtus::Attribute#inspect
Remove guard clause for ruby 1.9 and rbx
Update flay threshold
Add specs to Virtus::AttributeSet#[]= that remove some mutations

* There are still 2 other mutations, but this resolves the ones related to the
  string/symbol indexes.
Refactor Virtus::AttributeSet to be simpler

* No need to delete the original attribute from the indexes since they
  will get overwritten on the last line of #[]= anyway.
Refactor specs to use better mock names

* My normal convention is to have the mock name correspond with the let()
  block name, so that in the event something unexpected happens I can trace it
  back to the variable more easily.

  In this case I mostly followed that convention, except I felt it was more
  clear to use "original" for the original attribute because that spec was
  dealing with replacing an original attribute with a new one.
Remove dead code

* This line was not necessary for proper operation of the object. Perhaps it
  keeps the AttributeSet cleaner internally, but since it's encapsulated inside
  the object it's behaviour cannot be tested.

  This would only really be useful if the list of overridden attributes gets
  quite large. It probably won't in most cases.
Add specs to remove all mutations in Virtus::AttributeSet#[]=
Refactor Virtus::AttributeSet so index updating is handled by one method

* Renamed #merge_index into #merge_attributes to make it more clear that it
  merges the attributes into the set
Updated flay threshold
Remove test that was testing code that no longer exists in Virtus::ClassMethods
Update flay threshold
Fix specs to use proper method naming convention

* Instance methods should start with a "#" and singleton methods should start
  with a ".". It doesn't matter how the module/class is used, it matters how it
  is defined within the context of that specific module/class.
Add spec for Virtus::ClassMethods#const_missing