Expose 'languages' so they can be extended outside of the module

[jazziebgd]

I needed support for different scripts (i.e. sr-Latn and sr-Cyrl) in my code. Since those couldn't be added, I (slightly) modified the code so language data can be extended once module is required.

Now I can do the following:

Gta = require('google-translate-api');
Gta.languages['sr-Latn'] = 'Serbian Latin';
Gta.languages['sr-Cyrl'] = 'Serbian Cyrillic';

[coveralls]

Coverage decreased (-1.2%) to 89.706% when pulling b16ae1e on nwfw:master into 777d7db on matheuss:master.

[coveralls]

Coverage decreased (-1.2%) to 89.706% when pulling b16ae1e on nwfw:master into 777d7db on matheuss:master.

[codecov-io]

Codecov Report

Merging #31 into master will increase coverage by 0.26%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##           master      #31      +/-   ##
==========================================
+ Coverage    90.9%   91.17%   +0.26%     
==========================================
  Files           2        2              
  Lines          66       68       +2     
==========================================
+ Hits           60       62       +2     
  Misses          6        6

Impacted Files	Coverage Δ
index.js	88.23% <100%> (ø)	⬆️
languages.js	100% <100%> (ø)	⬆️

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[coveralls]

Coverage decreased (-1.2%) to 89.706% when pulling b16ae1e on nwfw:master into 777d7db on matheuss:master.