Add wordcloud directive

Added a wordcloud directive and JavaScript functions required to draw a
wordcloud. The next step is to retrieve wordcloud data from the server.
Add url mapping and view to retrieve wordcloud data

Added url mapping and view to retrieve wordcloud data for entity
wordclouds (given entity categories).
Display entity wordclouds on title page

On the title page (partial) entity wordclouds are displayed for selected
categories. The data is fetches asynchronously using a factory. The data
is not yet updated when the selected categories change.
Merge branch 'feature/wordclouds' into develop
Remove whitespace under graph on title partial
Add alias for es index

The name (alias) for the es index used was added as a setting to
settings.py. The name was also set to the new alias 'embem'.
Fix year2es and genre2es for titles with multiple subtitles

The year and genre data of titles with multiple subtitles were not added
to the ES index, because it is unclear what data to use. Now the details
from the original title are used instead.
Also added a utility function that extracts the year from a string using
a regular expression (to deal with years like 'ca. 1768').
Add the elasticsearch javascript client to the Angular app
Add basic search example

Added a pairs partial with a button that retrieves the first 50 results
from a match_all query and displays the text in a list.
Display graph for fixed pair

Changed ES query to retrieve aggregation data for a fixed pair. The data
is displayed in the interface after clicking the button.
Add parameters and parallel data loading

The interval for the buckets was added as a changeable parameter. Also,
the pair that should be displayed can be typed in a text input field.
Multiple pairs can be added to the graph and are loaded in parallel.
Display top 50 of entity words instead of top 25

Used as data for the lecture on December 1, 2014. (Not part of the pairs
visualization)
Show list of pairs that have been entered

The list of pairs will be used to remove data from graphs.
Display subgenre graph(s) for pair(s)
Add functionality to remove pairs

Pairs can now be removed. When a pair is removed, the relevant data is
also removed (this means a line disappears from the corpus timeline and
the subgenre graph for that pair also disappears).
Merge branch 'feature/entity-bigram-viewer' into develop