Update packages for binary install in Travis config
Update readme to mention preprint
doc: minor fixes
Merge branch 'feature/make-smat'

* closes #6
* feature/make-smat: (29 commits)
  docs: add cross-refs
  fudgefac -> epsilon
  choose random pairs (not all) from non_matching set
  rename random_pairs to neuron_pairs
  refactor calc_dists_dot_prods to return data.frames
  OUT.ATTRS are irrelevant for us
  tests for random_pairs
  When n=NA random_pairs draws all pairs
  export random_pairs
  calc_dists_dotprods(subset) defaults to NULL
  Document random_pairs
  Add random_pairs helper function
  doc fixes
  sty: mostly formatting
  Add tests for score matrix functions
  Fix default subset to use query neuron names as well as target in calc_dists_dotprods()
  Fix subsetting to not use subset function within calc_dist_dotprods()
  Fix character check for subset argument
  Import mlply from plyr (prevents NOTE in R CMD check)
  Add wrapper function for creating score matrix using smat functions
  ...
fix: actually use default non_matching_subset
new class scoringmatrix (inherits from table)
give neuron_pairs query and target arguments

* probably won't be much used, but does allow it to construct pairs of neurons with
  different query/target sets with ease.
Fix bug in neuron_pairs when query!=target

* also change to ignoreSelf arg for consistency
refactor: expand.grid call -> neuron_pairs
Add 20 random flycircuit neurons as test data
Fully worked example

* including a persp3d plot of resultant scoring matrix
Depend on nat >=1.5.12 for c.neuronlist

* this is just for the example which combines neuronlists with incompatible
  attached data.frames
score matrix -> scoring matrix for consistency