seen -> see (page 12)
an geometric -> a geometric (page 17)
fix beginning of Fibonacci sequence
Quaterly -> Quarterly (page 18)
edit: add definite article 'the' for readability
which [one] are -> which [one] is (page 22)
remove superfluous period (page 22)
Merge pull request #1 from clark-archer/sequences-typos

minor corrections through section 1.4