Output saving and loading

[matt-pharr]

Allows saving and loading of POPCON results. See #3.

[matt-pharr]

Complete! Adds both zipped and folder writes. Also added a nice json encoder that will write the arrays to a json in matrix form like this:

...
    "T_e_avg": [ 5.992478351528228e+00,  6.991224743449599e+00,  7.989971135370971e+00,  8.988717527292343e+00,  9.987463919213715e+00,  1.098621031113508e+01],
    "Paux": [
        [ 9.999900000000000e+04,  4.298035686709670e+00,  8.307956055381084e+00,  1.437947233187406e+01,  2.293129517036066e+01,  3.436463314822937e+01],
        [ 9.999900000000000e+04,  9.122156447862839e+00,  1.708537870739800e+01,  2.934679287320164e+01,  4.676969296194586e+01,  7.018439474721120e+01],
        [ 9.999900000000000e+04,  1.519422442200040e+01,  2.830537768749105e+01,  4.869983760487745e+01,  7.783881607889850e+01,  1.171285956899713e+02],
        [ 9.999900000000000e+04,  2.239544903361648e+01,  4.178338826869201e+01,  7.216747592746765e+01,  1.157567138960579e+02,  1.746777207626108e+02],
        [ 9.999900000000000e+04,  3.063481674093349e+01,  5.737859725189938e+01,  9.954321202398054e+01,  1.602330660520578e+02,  2.424360256275535e+02],
        [ 9.999900000000000e+04,  3.983877872842665e+01,  7.497747044008302e+01,  1.306604709455338e+02,  2.110342078199370e+02,  3.200858565663518e+02]
    ],
...

[nelsonand]

@matt-pharr This looks great!!