Add unit tests

[harrynull]

Changes:

• Add two new dependencies: gtest and nlohmann/json for unit tests.
• Add a unit test framework using gtest
• Remove .wav from .gitignore (for test cases)
• Fix travis.yml and add unit tests to travis.yml. Travis.
• Major changes to CMakeFiles.
• Add code coverage. See here.
• Fix JSON output (Remove trailing commas)
• Fix compilation of demos.

[codecov-io]

Codecov Report

:exclamation: No coverage uploaded for pull request base (master@d9182b1). Click here to learn what that means. The diff coverage is 78.64%.

@@            Coverage Diff            @@
##             master      #56   +/-   ##
=========================================
  Coverage          ?   42.58%           
=========================================
  Files             ?       27           
  Lines             ?     3454           
  Branches          ?      594           
=========================================
  Hits              ?     1471           
  Misses            ?     1983           
  Partials          ?        0

Impacted Files	Coverage Δ
src/lib_ccaligner/logger.h	65.07% <100%> (ø)
src/lib_ext/gtest/include/gtest/gtest-param-test.h	100% <100%> (ø)
src/lib_ccaligner/output_handler.cpp	19.06% <36.36%> (ø)
src/lib_ext/gtest/include/gtest/gtest-printers.h	41.37% <41.37%> (ø)
src/lib_ext/gtest/include/gtest/gtest.h	68% <68%> (ø)
...xt/gtest/include/gtest/internal/gtest-linked_ptr.h	81.57% <81.57%> (ø)
...xt/gtest/include/gtest/internal/gtest-param-util.h	85.31% <85.31%> (ø)
src/lib_ccaligner/ccaligner.cpp	86.66% <86.66%> (ø)
..._ext/gtest/include/gtest/internal/gtest-internal.h	88.88% <88.88%> (ø)
src/lib_ext/gtest/include/gtest/gtest-message.h	88.88% <88.88%> (ø)
... and 1 more

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[saurabhshri]

Thank you! That looks awesome already! :D I am merging, if any changes are needed, we can do it later. Thanks! :)