Fixes bug when debugger does not stops at the breakpoint set by method name

When you're setting breakpoint by method name with `break SomeClass#some_method` command,
`pry-byebug` converts it to filename and line number (line where `def some_method` statement is located). For some reason,
it does not works (`byebug` never stops at this breakpoint). Easy fix is to increment `method_object.source_location`
line number by 1 so that it points to the 1st line of the method, but it may not work properly for empty / one line methods.

It looks like you can pass method/class name instead of file name/line number to `byebug` directly which is exactly what
this PR is all about.
Merge pull request #15 from andreychernih/f/fix-method-breakpoint

Fixes bug when debugger does not stops at the breakpoint set by method name