Wrote introduction for PA1_template

Wrote the introduction text for the report in PA1_Template. Added the knitted
output (md and html) to the repository.
Total number of steps per day

Completed code and description for calculating the total steps per day. This
includes a histogram of total steps per day, annotated with study-wide mean
and median.
Average Daily Pattern & Minor fixes

This commit adds the average daily pattern (ADP) to the report, including
code to create a data.frame with the ADP, plotting the ADP as a time
series, and finding the time interval with the maximum daily steps
(plotting that as well).

It also includes some fixes to previous commit wrt aligning annotated text
(using hjust instead of manually adding/subtracting values from xintercept.
Refactoring of plotting and plot labels

Refactored the plotting in plot2 to match plot1 (saving to a gg object and
then printing). Refactored plot1 to use an object named p1 instead of
just p.

Added a main title and custom x/y labels to plot2. Bolded the titles for
both plots.
Filled in missing values, more plot tweaks

Completed filling in missing values, and plotted a histogram of the newly
contructed data.

Tweaked previous hitogram to show the mean & median values next to the
lines for them.