installation: new local FFT file cache

* Adds `populate-fft-file-cache.sh` helper build script useful to
  pre-download all files used in FFTs.  (closes #350)

* Amends installation instructions on how to use local FFT file cache.

* Amends all XML input files accordingly.

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>
UI: adds illustrations to "physics objects" page

* (closes #200)
docs: more detailed installation guide

* Adds more details on the installation, such as fast/incomplete option
  vs slow/complete option.

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>
docs: removal of unnecessary repetition

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>
CMS: update `cms-validated-runs.xml`

* Updates `cms-validated-runs.xml`.  (addresses #308) (PR #363)
CMS: fix for FFT in CMS Validated Runs

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>
Travis-CI: initial configuration

* Initial configuration for Travis-CI service.  Tests only whether input
  XML files are well formed; no other tests are being run at the moment.

Signed-off-by: Tibor Simko <tibor.simko@cern.ch>
histograms: add bin width input

* Adds bin width input.  (PR #386)
histograms: get value and apply bin size

* Gets value and apples bin size.  (closes #379) (PR #386)
histograms: rm scrolling as not needed

* Removes scrolling as it is not needed.  (PR #386)
histograms: file loading

* Loads other files and cleans up divs and rows.
  (closes #380)  (PR #386)
histograms: rendering on load

* Renders histograms no load.  (closes #382) (PR #386)
histograms: select/zoom for x axis

* Adds select/zoom for x axis.  (closes #387) (PR #386)
histograms: button styling clean up

* Cleans up the button styling.  (PR #386)
histograms: change in bin width drawing

* Changes how change in bin width is drawn.  (PR #386)