Introduced a new function `readLine()` that utilizes the byte buffer
together with `fgetc()` to read input from the STDIN. This enables
the REPL to read characters one at a time for validation & in a
safer manner where the buffer gets to be resized if it's full.
* While reading various files in the repo, just going ahead to
clean up some typos (for clarity of text).
* When calling `realloc()`, let the pointer be returned to the
first byte of the memory block after resize. Compiler warns against
not doing this too.
* In addition, rename the file uitls.c to "utils.c" which seems to
be the correct name in this case.
NOTE: I recompiled and tested the `./pocket` intepreter and it still
works as expected.
