perf: Conversion to Typescript (#183)

chore(package): Updating typescript  3.0.1  →  3.0.3
chore(package): Updating @semantic-release/git   ^7.0.1  →    ^7.0.3
chore(package): Updating @semantic-release/npm   ^5.0.2  →    ^5.0.4
chore(package): Updating semantic-release       ^15.9.8  →  ^15.9.12
chore(package): Updating codecov                 ^3.0.4  →    ^3.1.0
chore(package): Updating ts-jest                ^23.1.3  →   ^23.1.4
chore(package): Updating tslint-config-airbnb    ^5.9.2  →   ^5.11.0

Author: jdalrymple