completed stage 4 of about_arrays.rb

* pivotal tracker id [#75411406]
* learned about slicing arrays
* arr[a,b] slices the array starting at index a and contain b elements
completed stage 5 of about_arrays.rb

* pivotal tracker id [#75411406]
* learned the difference between arrays and ranges
* ranges can be turned into arrays with .to_a
* (1..5) is different than (1...5)
* three dots will not include the last element (5)
completed stage 6 of about_arrays.rb

* pivotal tracker id [#75411406]
* learned how to slice an array with a range
* array[a..b] will slice the array from index a to index b
completed stage 7 of about_arrays.rb

* pivotal tracker id [#75411406]
* learned that .push(element) will append element to the array
* learned that .pop will return the last element of the array
* .pop will also permanantely remove the last element from the array
Completed all stages (8/8) of about_arrays.rb

* pivotal tracker id [#75411406]
* learned the shift and unshift are like pop and push
* but they operate on the first element of an array, not the last