data-lens is not a dep of idris

lens is, but that isn't available in the binary repos of the old version
of Ubuntu Travis-CI runs.
Set the handles used for --client to use UTF-8

Previously they were binary-mode, so they used char8 “encoding”, taking
codepoint values modulo 256, leading to cryptic identifier mangling errors
when using idris-vim.
Fix typo in Idris network C code
add system to Effects.System as is
add system to Effects/System neweffects
Predicates for Prelude Strings
Merge pull request #1229 from LeifW/travis_deps

Don't bother installing data-lens
Merge pull request #1334 from Melvar/fix-ipc-enc

Set the handles used for --client to use UTF-8
Merge pull request #1336 from Heather/system

add system to Effects.System as is
Merge pull request #1345 from bmsherman/idrisNetFix

Fix typo in Idris network C code
Merge pull request #1352 from Heather/string

Predicates for Prelude Strings
Preliminary support for a :let command in the repl
Changed :let to work with an arbitrary number of `PDecl`s (though only one name at a time for now).

	It is no longer possible to leave off the type declaration. This will be fixed soon.
Create the CaseBuilder monad alias.
Add ReaderT to CaseBuilder.
Add getInaccessibleArgs.
Bring erasure info to the case tree builder.
Added some additional documentation for partial evaluation
Handling more forms of definition.

	 In particular, it should now be possible to define multiple names at once, and to
	 leave off type declarations when the type can be inferred.
Removed some commented-out code