Update readme with arbor web links (#361)
Update readme with arbor web links (#361)

Update README.md to use badge from updated Travis CI page, and updated references to the old nestmc-proto repository.
halfflat/arbor,halfflat/arbor,eth-cscs/nestmc-proto,eth-cscs/nestmc-proto,halfflat/nestmc-proto,halfflat/nestmc-proto,eth-cscs/nestmc-proto,halfflat/arbor,halfflat/arbor,halfflat/arbor,halfflat/nestmc-proto