Add error message rendering for bad posts

posts#create passes object with error messages back to post upon
validation failure

posts/index renders partial error_messages

error_messages checks if @post object contains errors and display them
if it does
Added validations for title/body length
Fixed horizontol spacing
Update model length validation format
Refactor: Extract form from error partial
Refactor: Fix horizontol spacing
Refactor: Do not abbriviate variables
No space inside block variable declarations
Refactor: Fix horizontol spacing