Code housekeeping.
Fixed return value of bit_path in int_tree

Compare to bit_path method in byte_tree.
Initialization of binomial_coefficients does not

depend on global static variables any more.
This fixes a valgrind warning.
Merge pull request #98 from simongog/code-housekeeping

Code housekeeping.
Added valgrid option for all test targets.
Merge pull request #99 from simongog/rrr-init-tables

Initialization of binomial_coefficients does not
Fixed LCA test.
Added deletion of code coverage info.
sigma is already in csa. Removed local member.
Fixed documentation of edge().
Increase code coverage of tests and replaced

rank_bwt -> bwt.rank
Fixed typos.
Fixed iterator and increased code coverage of test
Adjusted to new API.
Renamed smaller_lex_count to lex_smaller_count
Renamed constants namespace to conf
Added string_type to simplify extract method.
Addressed issue #101
Added iterators for WTs; fixed examples.
Added difference_type.