Score report functionality

[pebenbow]

In response to issue #14 , I have added a new function, getTestScriptReport, which accepts a given test script as an argument. It parses the test cases, counts them up and sums their point values, and generates a formatted report (seen below) that summarizes the test script.

This should be useful for auditing test scripts and quickly counting tests/points when configuring an autograder.

SIDE NOTE: Apologies for the convoluted commit history. I accidentally forgot to pull changes from tbrown122387:master before I began my work on this, so I had to go back, revert my commits, rebase from master, and reapply everything.

> report <- getTestScriptReport("scratch/lab0_tests.r")
==============================================================
TEST SCRIPT ANALYSIS REPORT
==============================================================

Script: scratch/lab0_tests.r

SUMMARY:
  Total test_that calls: 3
  Total criteria: 5
  Total points: 7

EXPECT_ FUNCTION USAGE:
  expect_equal: 3
  expect_true: 2

TEST DETAILS:
  Test 1: Create a vector with integers 1,2,3 (visible)
    Criteria: 1
    Points: 1
  Test 2: Create a character variable that says hey to Laurie (visible)
    Criteria: 2
    Points: 2
  Test 3: Dataframe has 32 rows and 11 columns (visible)
    Criteria: 2
    Points: 4

==============================================================

[tbrown122387]

Awesome, this looks great!